The Nursery (Part 10: Off with their heads! 4 of 5)

This is the fourth part of the post on grafting cacti and will consider whether to keep a plant permanently grafted or alternatively attempt to degraft it.

Once you have a grafted plant you might consider whether to keep it that way or whether to try and do something drastic. If you’re content with your grafted plant, so much the better. However, many collectors find their appearance unattractive and wish to either hide the stock plant or do away with it altogether. Of course, if the purpose of the grafted plant is to produce shoots or seeds it isn’t very important how it looks.

If the stock is low enough, it is often possible to hide it completely in a layer of grit if you have a deep pot. Care must be taken that the grit is of a large enough grain size so as to hold as little moisture as possible. Burying a stock in material that retains moisture for prolonged periods is to invite rot. But this way it’s possible to make a grafted plant appear as if it’s growing on its own roots. If the stock is too tall to do this, it’s possible to cut it off a little below the scion and set it to root. Once it sets roots it can be potted and the stock buried in grit. Beware though, that if the stock is old it might not form new roots easily.


Fig 15: Obregonia denegrii grafted on a very short stock that has been buried beneath grit. As can be seen, the Obregonia looks as if it grows on its own roots.

However, you might decide that you want to try and have the scion grow on its own roots. Sometimes the decision might be forced on you if e.g. the stock plant dies and you don’t have the option of grafting the scion on something else. Then it’s necessary to try and get the scion to form its own roots.

The practice of separating scion from stock is called degrafting. It isn’t any more difficult than taking a clean knife and cutting off the scion. At least, not in theory. It is certainly tempting to degraft when the scion has grown nice and big, though having the plant form its own roots can be tricky. Some species root only with great difficulty and may wither and dry up before putting out roots. Other species are more accommodating and will put out roots with ease. The scion should be cut off as far down as possible. If enough of the scion remains on the stock it is possible that it will put out shoots that can be removed at a later date. If the cut surface is very large compared to the size of the scion, it is quite likely that it won’t survive. The smaller the cut surface compared to the plant body, the greater the chances that it will survive. Some species might take months to put out roots, and during that time it’s vital that the plant has enough water reserves to last.

Many species are very reluctant to form roots and some species (like Ariocarpus) will never form a proper tuberous root after being degrafted. It is also fairly common to find that the roots formed by a degraft are not as strong as those formed normally by a plant.


Fig 16: Various degrafted plants. Upper left is Glandulicactus wrightii, Epithelantha bokei, Astrophytum asterias cv. Super Kabuto and Astrophytum capricorne var. crassispinum cv. Taiho. All set root except the A. cv. Taiho. Upper right shows Sclerocactus cloveria ssp. brackei of which all set root. Notice the unusual pink colour of the flesh. The lower image shows Geohintonia mexicana and Echinocactus polycephalus ssp. xeranthemoides of which only one of the Geohintonias has set roots after about 4 months.

In Fig. 17 you can see the various plants I degrafted and then placed in a tray for rooting. They are sitting in a medium consisting of cat litter (this particular cat litter is made of a form of diatomaceous earth and doesn’t clump or change shape when wet), and perlite (the white stuff). The tray was placed on a shelf above my two lamps where they’d be out of direct light but receive a good deal of bottom heat. After a few weeks I started to moist the cat litter and perlite slightly. The cut surface of the degrafts were all treated with root stimulating hormones in powder format, although I am unsure whether this helped at all and it’s not something I feel is needed at all. About 60% of the plants formed roots within 1-2 months, while Geohintonia (of which only one of four formed roots) needed 3-4 months. The Echinocactus, Blossfeldia and some of the Pediocactus failed to form roots.


Fig 17: Degrafted plants in a tray ready to form roots..

If you really want to degraft a scion, but are worried that it might not survive the process, it’s possible to cut off the top of the scion and either discard it or regraft it (or even just destroy the growing point). The remaining part of it will soon put out new shoots (even if it wouldn’t normally do so), that might in a few months’ time be easy to cut off with only a minimal wound and then set to root. All the while the old scion could continue producing new shoots for you.


Fig 18: Pediocactus peeblesianus ssp. fickeisenii sprouting profusely after having its head removed for rooting. The cut off head never formed roots, but as can be seen there are plenty of future prospects here for rooting in a few months’ time.


The Nursery (Part 10: Off with their heads! 3 of 5)

This is the third part of the post on grafting cacti and will look at why we graft plants.

There are many reasons for grafting cacti. One is to try and save a plant from certain death. Perhaps it is a weak plant that just does not seem willing to grow, or perhaps it’s a rarity or an old beloved family member suffering from some disease or maybe it’s started to rot. In such cases grafting may be the only alternative to throwing the whole thing in the bin.


Fig 8: This Sulcorebutia gemmae was stagnating for months after germinating. It seemed as though the growing point had been damaged somehow and it didn’t look particularly like surviving for any length of time. I decided to graft it and after only a couple of weeks it started growing. It appears to have found a new growing point as the new growth that can be seen actually broke through the old skin. It has turned into a large and healthy plant now.

Some species are notoriously difficult to keep for any length of time on their own roots, like most members of the North American genera Pediocactus and Sclerocactus. I suspect this has a lot to do with the fact that most collectors place them in a mixed collection with other cacti and give them much the same treatment as those other cacti. Those growers who try to emulate their native climate and growth pattern seem to do much better with them. Be that as it may, most members of these two genera are usually seen grafted because they are hard to keep alive otherwise.


Fig 9: Sclerocactus mesae-verdae in the foreground, and Pediocactus peeblesianus ssp. fickeisenii in the background. Both of these species are difficult to grow on their own roots.

The third main reason for grafting is to speed up growth. A lot of cacti are painfully slow to grow, a trait often seen in some of the most desirable species. Through grafting it’s possible to achieve greatly enhanced growth rates and flowering ability, as well as not having to take into account some of the species’ fickle nature by letting hardy stock plants deal with all the soil and water. Aztekiums are perhaps the slowest of all the cacti (at least A. ritteri), and not very easy to grow on their own roots either. Through grafting it is possible to grow them tens of times faster and bring them to flowering age years ahead of time. The drawback is that the plants being grafted will often lose their natural appearance.


Fig 10: On the left is Aztekium ritteri grafted on Eriocereus jusbertii, while on the right is Mammillaria luethyi grafted on Pereskiopsis. Aztekium ritteri isn’t the easiest plant to grow on its own roots, and is painfully slow to boot. Because of this it is most often seen grafted. Mammillaria luethyi isn’t particularly difficult, but is most often seen grafted primarily because it is a cryptocarp (it hides its fruits within the plant body for years) which means that seeds are seldom available, so the easiest way to propagate it is through grafting cuttings such as the above.

The fact that grafted plants so often lose their natural appearance is probably the biggest drawback for me personally, as I am not a particular fan of how some species turn out looking when grafted. Some species look fine when grafted and don’t deviate much from how they’d look on their own roots, but some species (like Aztekium) can almost look like different species altogether compared to their brethren growing on own roots. There is also a sense of achievement in successfully growing some of the more difficult species that just isn’t found when grafting them.


Fig 11: The two images show the same specimen of Aztekium hintonii. As can be clearly seen, it grows vigorously and flowers profusely, but its appearance is not quite natural.

As touched upon above, achieving flower production much sooner than would otherwise be possible is an important reason for grafting. Pereskiopsis is perhaps the most widely used genus for grafting seedling cacti. Its stems are thin and suitable for very small plants, and its growth is simply explosive. I’ve never tried growing Pereskiopsis to their full potential, but if given enough heat and light they can probably enjoy almost continuous wet/moist soil which would be the death of most ordinary cacti. Properly grafted on a sizeable Pereskiopsis 10-15 cm high with full green leaves in optimal conditions, a seedling no more than 2 weeks old can probably achieve flowering age within a matter of 2-3 months at a size it might otherwise need half a dozen growing seasons to achieve on its own roots. I’ve never achieved anything close to that personally, but then I’ve never grafted on properly sized Pereskiopsis in ideal condition enjoying near limitless quantities of water.


Fig 12: Lophophora alberto-vojtechii grafted on Pereskiopsis. The plant was grafted around 6 months after germination as it didn’t grow particularly well. 4 months after being grafted, the first bud appeared (left). The middle image shows the flower, and the right image shows the plant ca. 1 year after originally grafting it. It’s the size of a 2€ coin which is probably about as big as the plant would ever get in nature.

Achieving a much more rapid flower production than would otherwise be possible is very beneficial when trying to set seed on rare species. Aztekium ritteri is a fairly common species in seed lists, but if you want to get seeds on plants growing on their own roots, you might have to wait up to a decade. Grafted, the same species might oblige within a year of being sown. Grafted plants generally produce more flowers and are usually able to bear more fruit to maturity. In some Asian countries (particularly Japan and Thailand) they’ve perfected the art of grafting, and some of the master growers of Astrophytum can raise several generations in a couple of years with the purpose of hunting for new and rare hybrids.


Fig 13: Sped up flower production on Lophophora fricii and L. koehresii. None of these plants are more than a year old.

Another reason to graft is if you sow seed and get a weirdo seedling coming up. Perhaps it is fasciated (crested), monstrose (abnormal growth pattern), variegated (with parts of the body having less chlorophyll), or abnormally proliferous (where every areole produces a new shoot), or perhaps it is a particularly striking hybrid. In such cases you might want to hang onto it. However, such plants are often not as strong as their normal brothers and sisters, so grafting them is a good way to ensure they stay alive. Such plants hold a great fascination for some growers who are willing to pay a lot of money for good specimens. Some plants lack chlorophyll altogether, like the well known red or yellow grafts that are often seen in supermarkets (Gymnocalycium mihanovichii and Chamaeocereus hybrids respectively). These plants wouldn’t survive on their own (seeing as they lack chlorophyll) and must be grafted to survive. It is even possible to make something akin to a decoration by grafting several different plants on one stock plant with many shoots.


Fig 14: Variegated Lophophora diffusa. This plant might not have survived on its own roots for very long, and even if it had it would likely never have become a “strong” plant.

Cereus peruvianus 'monstrosus' 001 (26.05.2006)

Fig 15: Cereus peruvianus ‘Monstrosus’ has a growth habit where the ribs form in an irregular manner. This plant isn’t grafted though, and manages perfectly fine on its own roots.

The Nursery (Part 10: Off with their heads! 2 of 5)

This is the second part of the post on grafting cacti and will look into more detail about the technical bit of actually grafting a cactus.

The one single thing about grafting that is of utmost importance is cleanliness. If you set to with a rusty old knife held in dirty fingers, you’re asking for trouble. Clean tools should be used, and they should ideally be disinfected at every turn (at least after every major operation) with rubbing alcohol or some other disinfectant that won’t leave traces. As with clean tools, it is naturally also vital that the cut surfaces are both clean and free of any rot, sickness or debris. Your working area should be clean and somewhere out of the sun and the elements.

For cutting larger plants I prefer either a sharp knife with a comfortable handle or a snap-off knife. For seedlings I think razor blades work best. Depending on what kind of plants you’re working with, some form of protection might be beneficial. When working with Pereskiopsis I like to use a sheet of aluminium foil folded several times to make a sort of finger-protection-device allowing me to hold the plants without having to suffer their devilish spines. A good pair of tweezers will often come in handy too. Rubber bands are handy when it comes to larger grafts to push the scion and stock together if the scion is of the globose kind and the stock plant isn’t too tall. It’s easy to push the scion off the stock with rubber bands so it’s important to be careful when using them. Weights of different kinds can also be used to put pressure on the scion so that it properly fuses together with the stock.


Fig 4: Various tools for grafting.

When grafting plants that have started rotting (in an attempt to save them), it is necessary to cut away all the diseased or rotting parts of the scion, even if it means cutting it so short that grafting becomes almost an act of futility. Almost all cacti are a nice and healthy green inside (the flesh of some species has a more yellowish or reddish hue), so any traces of black/brown or discoloured spots or marks visible on the cut surface means you have to continue cutting. And for each cut it is necessary to disinfect the cutting tool so as not to unwittingly spread infected material to healthy tissue. The cutting tool should be very sharp and, if possible, the cut should be made in one or two smooth motions and not in a sawing fashion. It’s also helpful if the cut is as straight as possible.


Fig 5: Seedling grafts on Pereskiopsis. Seedlings can easily be grafted from around 2 weeks old.

When grafting seedlings it is easiest to use a razor blade. The seedling can be held between your fingers while carefully slicing it in one motion. The top of the seedling will be sitting on the razor blade and can easily be pushed or nudged over to the surface of the stock plant. Once placed it should be gently rotated or wiggled a bit to remove any potential air bubbles trapped underneath, and care must be taken to place the scion so that it is in contact with some of the vascular bundles of the stock. No weights are usually needed to provide pressure on the seedling against the stock, as the sticky sap of the stock will be enough to keep it in place.

When grafting anything larger than seedlings or very small plants it is useful to shape the surface of the stock a little bit before grafting (see Fig 6). If areoles are left on the stock plant right by the cut surface, it can lead to shoots forming from them that might eventually push the scion off. Cutting away the outermost sides of the stock in an angular fashion to remove areoles will help the union be successful.


Fig 6: Image 1 shows an Eriocereus jusbertii shoot (a common stock plant). Image 2 shows the top of the Eriocereus removed. Image 3 shows angular cutting of the sides to remove the topmost areoles. Image 4 shows the top and bottom of the plant “ready for grafting”. On image 4 on the “stock”, notice the tiny bit of debris at the centre of the plant. This is something that would have to be removed before grafting. Image 5 shows the finished “graft”.

It’s extremely important that none of the cut surfaces dry out when grafting. If they do, a new cut has to be made. The stock should be cut first and, unless it’s a seedling graft which is very quick, to protect the cut surface either the top that was cut off should be put back in place until the scion is ready or a small slice of the stock should be cut and placed on top of the wound. Then the scion is cut and quickly placed on the stock (if a small slice of the stock was placed to protect the wound, be sure to remember to remove it). The scion should be lightly pushed down on the cut surface of the scion with the fingers and wiggled around a little bit to remove any potential air bubbles that might be trapped between scion and stock.

The scion gets its nutrients from the vascular bundles of the stock plant. It is therefore necessary that the vascular bundles of both parties are aligned such that there is an overlap. If they don’t align very well it is likely that the growth of the scion will be poor, which is why it is important that particularly the scion does not greatly outsize the stock . When grafting seedlings or plants so small that they do not cover the stock’s vascular bundles, they should be aligned so that they sit astride a section of the stock’s vascular bundles. This will allow them to receive sufficient nutrition from the stock. When grafting seedlings on thin Pereskiopsis stock this is usually nothing to worry about.


Fig 7: In this close-up of image 3 in Figure 6 above, it’s easier to see the different parts of the plant’s internal structure (simplified). The epidermis is the outer skin. Immediately inside is the cortex which constitutes the largest part of the flesh in cacti. Then comes the vascular bundles which can be seen above as a ring separating the cortex and the pith. The pith is the circular centre of the plant which is somewhat denser than the flesh of the cortex. In some species, like most opuntias, the pith and vascular bundles form an oval instead of a circle. When grafting small plants or seedlings on Opuntia, it is often possible to graft several plants on the same cut surface because of this.

After the scion has been successfully placed on the stock, it should be weighted down (unless it’s a seedling) either with weights or e.g. with rubber bands over the scion and under the pot. Be sure not to squeeze the scion to death and, if using rubber bands, take care not to push the scion off the stock through poor placing of the rubber band (which unfortunately is all too easy to do). With smaller scions it is often a bit more tricky to use rubber bands, and some form of weights might be better. E.g. a small coin or thin sheet of glass or something similar might be placed on top of it, balanced against something else. It’s also possible to wrap cling film around the scion and stock to provide both a moist environment as well as some pressure.

Once the graft has been made the happy couple should be place out of direct sunlight and preferably in a somewhat humid area. A few days under plastic or in a propagator, or on the lower shelf of the greenhouse should suffice to seal the deal. Grafted seedlings benefit from a slightly more humid environment in the first few days to secure the union. If the graft is successful, the scion and the stock will have fused together within 1-2 weeks of grafting and growth should be visible within a few weeks (less with seedlings). At this point the pair should still be treated gingerly, as it’s only after a couple of weeks that the union is so secure that a mere bump or something similar won’t easily dislodge the scion.

The Nursery (Part 10: Off with their heads! 1 of 5)

Taking inspiration from a recent comment one of my readers made about grafting, I thought I’d write a post about it. In fact, I’ll write five. Some of the posts I’ve written before have become far too big so, instead of writing one monster post, this time I thought I’d split it up in more manageable parts. The first three parts will be about the how and why of grafting, the fourth part will be about the choice of either degrafting or keeping a plant permanently grafted, while the last part will deal with some of the different grafting stocks that are in use.

Grafting cacti is usually very easy. The family is uncommon among plants in that almost every cactus can easily be grafted on members of only distantly related genera. I suppose the genus Pereskia is an exception to this, being hardly succulent at all, although I’ve never actually tried grafting them. While it might technically be possible to graft any cactus on any other cactus, not all cacti are suitable as stock plants.


Fig 1: Various grafted plants and some different stocks.

With grafting, the two main players are the stock and the scion. The stock is what one uses to graft on, while the scion is the bit that’s being grafted. This will usually involve the stock losing its head, while the scion is separated from its lower body. The scion is placed atop the stock and, once the two parts fuse together, a more or less happy marriage ensues. For as long as the union lasts, the scion will draw all the nutrients it needs from the stock. The stock itself should be in perfect health, it shouldn’t be too big or too small with regards to the scion, and the graft should only be made on new and healthy tissue.

The most straightforward and common way to graft cacti is to cut both stock and scion “horizontally” across the body so that the scion will fit nicely on top of the stock. As mentioned in the previous post, it’s important that there isn’t a huge size difference between the two parts. However, some cacti that grow long thin (or thin-ish) shoots that might be difficult to graft “standing up”, can be cut laterally along the body and then pressed down on the horizontal surface of the stock. Areoles on the scion will then go on to produce shoots. The members of the genus Echinocereus that were formerly known as Wilcoxia are perhaps candidates for this method.


Fig 2: Grafted plants on Pereskiopsis and Selenicereus.

It’s also possible to graft tubercles of some species. I have attempted to do this with an Ariocarpus trigonus that suddenly decided to head for the great desert in the sky. A few healthy tubercles were left, but not enough to graft normally, so I decided to try and graft a couple of the tubercles. Only one is still alive (after three years) although it hasn’t done much except not die. The idea is that the tubercle will be able to sprout a new growing point from it’s base from which the plant will be able to regrow and form a new normal looking Ariocarpus. Apart from Ariocarpus, I’ve read that certain mammillarias and some members of other genera are able to regrow from a single tubercle in this way. It remains to be seen whether my attempt will ultimately prove successful.


Fig 3: Ariocarpus trigonus tubercle grafted on Opuntia compressa.

The top that was removed from the stock may be set to root or be discarded. To avoid the possibility of virus infections it is recommended that stocks be grown from seed and only used once, i.e. no parts of it are reused. As far as I know I have never had any trouble with viruses on stock plants, but then virus infections are a very little studied phenomenon in cacti. It may be more widespread than we think, or the danger of it may be very exaggerated. I have often used stock plants several times and often taken cuttings from older stock plants to use. And for some stock plants, such as Pereskiopsis, seed is hardly, if ever, available. The remains of the scion may also be left to continue to grow and set new shoots unless it’s a rescue job, of course.

It may seem irreverent to cut and slice our plants open, but a lot can be learned from it. It can be fun to try and see how quickly you can manage to grow a species, or you might be interested in trying out different stock plants to see which suits best for a particular species. Grafting can allow you to witness your plants flowering years ahead of time, or let you save just that one very special plant that has begun to rot. Grafting can be a method to grow plants you might not otherwise be able to grow on their own roots, or you might simply find grafted plants attractive. Whatever the reason for grafting, it is certainly a worthwhile practice to know and understand.

The Nursery (Part 9: Soil components)

In this post I will expand upon Part 4 of this series and go into more detail about the various soil components I currently use (to a larger or lesser degree) for my cacti and succulents. I will first discuss organic and inorganic soil, and then go through the different soil components I use to a larger and lesser degree.

Organic or inorganic soil

I prefer an inorganic soil to an organic based one for most of my plants when they are past the seedling stage. There are several reasons for this. One is that most of the species I’m currently growing (and most of those I like the best) are susceptible to overwatering and thus require a very free draining soil which doesn’t retain moisture for a long time. This is easier to achieve with an inorganic soil than an organic one. Another is that inorganic soils reduce or eliminate the risk of several pests such as the sciara fly and (I believe) the root mealy bug. A further reason is that an inorganic soil with little or no freely available nitrogen will more easily induce a compact form of growth, compared to organic based soils in which plants more easily stretch.

Yet another reason is that with an inorganic soil it is possible to grow the plants completely without the use of fertiliser and have them look very natural (approximating the “natural” look in habitat), though I am not currently growing any of my plants without fertiliser. If one chooses to grow the plants without fertiliser, one must take care to choose a soil mix that contains all the nutrients the plants need. In the journal Acta Succulenta which is a free online journal available for download from their website Acta Succulenta, there is a very interesting article in the second publication of this year discussing a method of growing cacti they call WIG (Wild Grown). A similar method is discussed at length in a Xerophilia Magazine special edition called “The Rock Eaters”, which is also an excellent guide to the use of inorganic soils. It is available for download from their homepage Xerophilia. Personally I find plants grown this way to look more beautiful than plants seen grown in organic soils which tend to become more elongated or bloated – though this also depends on the species.

Example of an inorganic soil.

A very interesting article which appeared on the BBC a few years ago ago reveals how (many or most?) cacti live in symbiosis with bacteria in the soil that break down rocks around the roots allowing them to absorb nutrients that wouldn’t otherwise be available. It also shows how the plants incorporate these bacteria into their seeds. This explains how it is possible to achieve excellent results by growing cacti in 100% inorganic soil without using fertiliser.

I grow almost all my current North American species in an inorganic soil. Only about one tray with North American species are potted in an organic based soil in order to compare their growth with similar species grown in an inorganic soil. So far the plants grown in the inorganic soil seem to do better and stay more compact. Since they all share the same level of light and amount and frequency of waterings, as well as the amount of fertiliser given and soil volume, and they’re all the same age, I think the only thing of importance that separates them is the soil composition. The ones in an organic based soil (particularly Epithelantha and Mammillaria) all tend to elongate and become more bloated compared to those grown in an inorganic soil.

I do grow some species in an organic based soil because I feel they do better with some organic matter. Chiefly among those are the South American species such as Rebutia, Sulcorebutia, Lobivia and Frailea (and any other South American species not growing in particularly arid environments). I kept my Frailea asterioides in an inorganic soil for some time, but they grew only very slowly. I keep my Discocactus horstii in an inorganic soil, however, and they are all growing very well – though in nature they grow in almost pure quartzite sand and gravel.

Example of an organic soil. This one is based on coir.

What you decide to grow your plants in will depend on your own beliefs and ideas on which soil is the best, which soil components are readily available where you live, the cost of the various soil components, and the types of species you like to grow. There is no answer to which soil is the best and almost every book on cacti will offer different advice. One should also keep in mind that cacti grown in pots are wholly removed from their natural habitat and must be treated accordingly. Adaptations must be made to account for a (probably) much reduced living space for the roots, a different fungal and bacterial flora in the soil, and of course usually a vastly different climate.

Just like seeds will readily germinate in commercial cactus soil mix, so will most species grow happily in the same mixes. They will be more prone to rotting though. If using such a mix I would definitely recommend adding extra grit such as perlite or gravel to increase the drainage.

Soil components

There are a plethora of different soil components available, and the following simply represent the various things I have personally used and have experience with. As I said above, there is no “correct” soil and one grower will have positive experiences with one soil while another will not. 


The only soil component that I would actively advice against is peat. I discussed my reasons for this in Part 4, but to summarise very shortly: peat takes a long time to dry out and when it has first dried out it is very difficult to re-wet; it is a magnet for the sciara fly, and the root mealy bug too, I believe; it quickly becomes compacted and reduces the amount of air available to the roots; it clings to the roots so that during repotting it is difficult to remove all of it without damaging the roots; it often leads to a less developed root system; it contains a high amount of nitrogen (and is often augmented with fertiliser high in nitrogen) which can lead to root burn and also abnormal growth; and finally it is not very environmentally friendly as the extraction of it destroys natural habitats for many species and can take centuries or millennia to reform, as well as leading to increased greenhouse gas emissions through the release of CO2 and MH4.
The only reason to use peat in my opinion is if you are just starting out with the hobby and only wish to keep a few species in the window sill, or if alternatives are very hard to come by.


I’m only mentioning this very quickly as it is probably the most commonly used ingredient in organic based soils. I do not use it myself because I have not found a good manufacturer yet. In Norway there is as good as a monopoly when it comes to garden centres, and by far the biggest (and almost only) garden centre does, to the best of my knowledge, not sell composts – at least not any that are useful for growing cacti. Some local garden centres or plant schools may still sell quality composts though, again, I have not really come across any. A good quality compost is probably the best ingredient to use in an organic based soil because it provides most of the nutrients the plants need which reduces the need for fertiliser.


Coir is fibres extracted from the husks of coconuts. It is a far better alternative than peat for organic soil mixes. Among the advantages are that it is naturally free of bacteria and fungi, it is easily rewettable after drying out, it doesn’t compact like peat, it doesn’t cling to the roots, and it rarely clumps together (and if so the clumps are very easily crumbled apart). Among the disadvantages is its lack of nutrients which means a greater need for fertiliser, its light weight (which in some cases can be an advantage, though), and the fact that it is poor in calcium and magnesium. A lack of magnesium is a problem for all plants, but a lack of calcium is also especially negative for most cacti. This can be remedied by adding calcium and magnesium through fertiliser or by adding rocks such as dolomite (containing both magnesium and calcium) directly to the soil. Dolomite is an excellent rock to add to the soil for most cacti regardless of whether you use coir or not.

Finally it is also important to check whether the coir you have has had fertiliser added to it. As with peat mixes, I believe fertiliser is often added to bags of coir too.

Coir. A very good substitute for peat.


Leca (light expanded clay aggregate) is produced artificially by heating clay at very high temperatures. It improves drainage and with it’s honeycomb structure it also retains a lot of air. Leca usually comes in sizes too large to be of much use in small to medium size pots. In large or very large pots it would be useful as a soil additive. For smaller pot sizes the main use would be to increase drainage by placing a shallow layer of leca pebbles in the bottom of the pot. It can also be useful as top dressing in larger pots, though it should ideally be washed before use to remove the dust coating the pebbles.
Leca pebbles are usually too large to be of much use in small and medium size pots.

Expanded shale

As with leca, this product has also been fired at high temperatures in order to make it expand. Shale is a naturally finely laminated (fissile) sedimentary rock consisting of clay and silt size particles. When it expands this structure leads to the rock becoming very porous. It has similar soil improving characteristics as leca, only more suitable for small to medium size pots. I have used two sizes, a 4-8 mm grain size and a 1-3 mm grain size. For smaller pots the larger grain size is still a little on the big side, but the smaller grain size is ideal. Similarly to leca it doesn’t lose shape or disintegrate. The larger size expanded shale is also useful as a top dressing.
Expanded shale, grain size 4-8 mm.

Expanded shale, grain size 1-3 mm.

Crushed lava

This soil additive is, as the heading says, crushed lava. It is naturally a very porous rock increasing drainage and improving soil texture. It is heavier than artificially expanded materials and so adds a bit of weight to pots (which might otherwise become a bit light if a lot of material like coir or perlite is used). The grain size I have used is 2-8 mm, which is on the large side for small pots. It is also useful as a top dressing, though its sharp edges may cut or scrape the plant as it grows and expands.
Crushed lava, grain size 2-8 mm. 


Pumice is a highly porous volcanic rock and a very good soil additive. Much like the materials mentioned above, it improves soil drainage and structure, as well as retaining water and air which is slowly made available for the roots. It comes in many different sizes, though – like the above materials – the larger sizes are less suitable for small and medium pots.
Pumice, grain size 5-15 mm.

Pumice, grain size 2-5 mm.


Zeolite is a very porous aluminosilicate mineral. It occurs naturally but can also be produced artificially. I use a natural form which comes in gravel size. It is widely used as an adsorbant in various industries. It absorbs a lot of water and, due to its molecular structure, can retain various elements. The idea behind using it in the soil is that its capacity to adsorb and retain elements will lead to these becoming available to the roots as the water stored in the mineral is released as the soil dries. However, I am uncertain if it actually works as intended in the soil. To me it seems like the zeolite doesn’t really leach these “trapped” nutritional elements as the water drains from it, but rather builds them up to the extant that salts crystallize on the surface. If this is, in fact, the case then its usefulness is very limited since its other chief value of retaining water is achieved by lots of other materials. One other use would be top dressing for certain plants, as its green colour is very nice.
Zeolite, grain size ca. 5-10 mm.

Crushed terracotta

This is another useful material to add to soil. Gravel size it acts to improve drainage and soil structure, as well as absorbing water which is then slowly released into the soil as it dries. In finer sizes it is useful as top dressing and soil component for seedlings. Made from clay, there are also a lot of various minerals available for the roots to extract.

Crushed terracotta, grain size ca. 4-6 mm.

Crushed terracotta, grain size 0-2 mm.


Clay can be a very useful additive in small components. Because of its very fine grain size it can reduce drainage in the soil and retain too much water if there is too much clay in the soil. It contains a large amount of elements however, and in small amounts it is a useful additive. 
As can be seen on the picture, there are many large clumps of clay. These can be problematic in the soil as they can create areas where more water than desirable is accumulated.


Akadama is the name of clay pebbles that occur naturally in Japan. They are widely used in the bonzai industry because of their ability to absorb a lot of water and retain their structure as they dry, and repeat the process over and over. It improves drainage and aeration in the soil, as well as providing a lot of nutrients. It is an expensive product, however.
Akadama clay pebbles, grain size ca. 2-4 mm.


Sand is a much used soil additive. Added to organic mixes it helps improve drainage and soil structure. However, in inorganic soils I believe it has a tendency to move around and cling together with other sand particles creating zones with more sand, which leads to reduced drainage. In many cases it may be better to use either coarse sand or fine gravel which will do the same job as sand, but not potentially impact negatively on drainage.
Sieved filter sand, grain size 1-2 mm. 


Gravel, particularly as crushed rock, is a useful soil additive to improve drainage and structure. It is probably the cheapest inorganic material too (along with sand). If you want to grow in a completely inorganic soil it is perfectly possible to do so by combining gravel from different rocks and minerals in the soil to provide all the nutrients the plants need. For seedlings and in small pots it may be of less value as smaller size material will probably be better, but in medium to large pots it is an excellent additive. It is also excellent as top dressing.
Crushed phyllite, grain size ca. 5-10 mm. 

Diatomaceous earth

This is a light, porous sedimentary rock consisting of fossilised remains of diatoms. It consists mainly of silica and some aluminium. It comes in a range of grain sizes from dust all the way up to gravel size, and has a wide variety of uses. It retains water and nutrients which is slowly released as the soil dries. I don’t have a lot of experience with this material but it seems a good soil additive.
Diatomaceous earth, grain size 1-3 mm.


This is an extremely light volcanic material that occurs naturally, but is used only after being processed by firing it at very high temperatures, expanding the material greatly. It helps improve drainage and soil structure, while having a fairly low water retention capacity. It is a very useful material and fairly cheap, however its low weight can be an issue as the perlite particles will very easily float to the surface of the pot – especially if watered from above.
Perlite, grain size ca. 3-6 mm.


Vermiculite is a naturally occurring siliceous mineral that expands greatly when fired – like perlite. After being processed in this way it becomes a very useful soil additive to improve drainage, for retaining water and nutrients, and for increasing soil structure. While also extremely light, it doesn’t float to the surface like perlite.
Vermiculite, grain size ca. 3-8 mm.

Mineral magic

This material is something I don’t quite know the usefulness of as a soil additive. It is a dust-like yellowish material that is supposed to contain 65 different minerals and 60 % of the content is supposed to be water soluble silicates. Spread around the top of the soil it is supposed to prevent algae and fungi growth, while as a foliar spray it is supposed to act as an insecticide. As a soil additive I don’t know whether it is a very useful substance considering all the minerals it supposedly contains, or whether the dust size grains merely leads to reduced drainage. It is supposed to increase the cation exchange rate in the soil which should lead to more nutrients being available for the roots. I add a little bit of it in my soil mixes. If it does what it claims it should be a useful additive. 
Mineral magic. With a saguaro (Carnegiea gigantea) pictured on the label it surely can’t hurt to add to the soil!


In the end, it isn’t really critical to use one particular soil component or the other. I have tried out quite a few because I’ve been curious about how they work, but many of the materials talked about above do much the same thing. The important part about soil is that it should be well drained and have a good structure with plenty of air. Whether this is accomplished through an inorganic soil or an organic based one isn’t that important. The amount of the various materials is only really important when it comes to growing plants without the use of fertiliser at all, since then one must strike the right balance in the soil between the various components so that all essential and beneficial nutrients are provided.
The size of the collection and which materials are most easily (and cheaply) available will usually be the deciding factors on which soil components to use.

The Nursery (Part 8: First flowers)

For once there’ll be a post with less text and more images! I feel flowering is one of the best ways to see whether your plants are doing well. If they are of flowering age and their growing conditions are good all cacti will generally be happy to produce flowers. If not, they will be much more reluctant to flower – although flowering can also be induced by high levels of stress or such things as manipulating the plant’s hormones. As I mentioned in the post about fertilisers and additives, I do add a few drops of certain plant extracts with most waterings that are supposed to increase flowering, so it’s possible this may have had an effect on some of the species.

Seeing the little plants develop from seedlings to flowering plants is very rewarding and one of the best parts of the hobby. I plan on giving them about a month’s rest in December to try and induce more flowering. The oldest plants will then be about 16 months old and I think a lot more will be ready to flower at that point.

Pseudolithos mccoyi

The first of the plants I sowed in late July/early August 2013 to start flowering did so in February, approximately six months after germination. The one to start it all off was Pseudolithos mccoyi. I have no experience with this genus so I don’t know whether it usually starts flowering at a very young age. Since they began flowering in February they’ve kept it up ever since, and now 9 months later they’re still at it. I have no idea how to pollinate them. As far as I know it’s done by flies in nature (though the flowers don’t smell anything), but it doesn’t seem like any flies have visited them over the past months. I don’t know who this species was named for, but I like to think it was Star Trek’s Dr. Leonard McCoy!

Pseudolithos mccoyi starting to flower at six months old. The top dressing is crushed lava and the plants are blending in very well!

A closer look at the flowers of Pseudolithos mccoyi. This plant is 14 months old here, and it and its brethren  have been flowering non-stop for 9 months so far. The flowers are tiny at no more than  5 mm wide. Some of the P. mccoyi  (such as this one) have developed a very nice greyish bloom on the epidermis.

Turbinicarpus longispinus nom. prov.

The second species to start flowering was Turbinicarpus longispinus at 7 months old. The name is a nom. prov. (nomen provisorium) meaning a provisional name, and as far as I know has never been validly published.

It is supposed to be a synonym of T. rioverdensis ssp. paolii, which is again a synonym of T. rioverdensis according to Hunt et al. (2006), Pilbeam & Weightman (2006) and Zachar (2004). Furthermore, the same authorities place this taxon as a subspecies under Turbinicarpus schmiedickeanus as T. schmiedickeanus ssp. rioverdensis. This should then be the current name of the species.

However, if T. longispinus is indeed a synonym of T. rioverdensis ssp. paolii, then according to Donati & Zanovello (2005) it should be called T. klinkerianus ssp. schwarzii as they claim it is just a re-description of T. schwarzii which they place under T. klinkerianus. If they are correct, the name of the species according to Hunt et al. (2006), Pilbeam & Weightman (2006) and Zachar (2004) should then be T. schmiedickeanus ssp. macrochele since they place T. schwarzii under synonomy with this taxon.

So…what to think? I now have the following options depending on which authority I’d like to follow: T. longispinus nom. prov., T. rioverdensis ssp. paoliiT. rioverdensisT. schmiedickeanus var. rioverdensis, T. schmiedickeanus var. macrochele and T. klinkerianus ssp. schwarzii. A Gordian knot if ever I saw one!

I am not particularly inclined to agree with Donati & Zanovello (2005) as I think their recombinations of species and way of classifying species is a bit odd. But what exactly to call it I’m not sure. It seems to me to be similar to all of the above mentioned species. I will have to delve into the matter a bit deeper before deciding on anything, so for now they’ll stay as T. longispinus. It’s a nice plant though!

Turbinicarpus longispinus in bud at 7 months old. The spination is variable, and not all the plants have longer than usual spines. This plant is about 1,5 cm in diameter.

Detail of the flower of Turbinicarpus longispinus. The flower is approximately 2,5 cm tip to tip.
Turbinicarpus longispinus at 11 months old. It was cross pollinated and, as can be seen, the fruit has just split open revealing the seeds inside. This plant, ca. 2 cm in diameter, does not have particularly long spines.

Mammillaria roemeri

The next one out was Mammillaria roemeri at 9 months old. Originally only one plant germinated, but some months later another seedling appeared to keep the first one company. It produced just one flower and hasn’t attempted to flower again since. It is a relatively new discovery and according to Hunt et al (2006) it is likely just a neotenic (retaining juvenile characteristics into adulthood) form of Mammillaria lasiacantha. It certainly seems to be a neotenic form, though whether it is just a form of M. laiacantha I feel is too soon to say (at least for me).

Mammillaria roemeri in bud. The plant is about 2 cm in diameter.

Mammillaria roemeri with the flower wide open. It’s a very nice shade of pink with a slightly darker mid stripe. The flower is about 1,5 cm in diameter.

Adenium multiflorum

After this, Adenium multiflorum decided to go next at 12 months old. I can’t honestly say that it looks very different in appearance compared to my A. obesum or A. arabicum apart from being slightly taller and more elongated, but maybe it will in age.

Adenium multiflorum with buds. It’s about 15 cm tall.

Adenium multiflorum with lovely coloured flowers. The flowers are ca. 6 cm in diameter.

Mammillaria hernandezii

Mammillaria hernandezii was the next one out at 11 months old, and put on quite a show for about a month. About seven different plants produced flowers, though none of them produced more than one. I kept pollen in the fridge and pollinated every flower so I expect some of them will have set fruit, though it’s difficult to tell since they are cryptocarps, keeping the fruits hidden in the plant body.

The first Mammillaria hernandezii to start flowering. As can be seen there are several plants with buds. The plants are approximately 1,5-2 cm in diameter.

Close-up of Mammillaria hernandezii with flower. The colour is very nice and the camera doesn’t quite do it justice. The flowers are ca. 2 cm in diameter.

Mammillaria plumosa

At the same time Mammillaria plumosa began flowering, also at 11 months old. It’s a very pretty plant and while the flowers aren’t as spectacular as in M. hernandezii, they are nevertheless charming. Both these species usually flower late in the year from autumn to winter, so I was pleasantly surprised not just that they flowered but that they flowered in September already. A lack of sunlight is usually the cause for their lack of willingness to flower in Northern Europe, so I take it as evidence that they’re receiving sufficient and good quality light from my artificial lighting.

Mammillaria plumosa with a pretty little yellowish flower just starting to open. The plant is ca. 3 cm in diameter.

Mammillaria plumosa with the flower wide open. The flower is ca. 1 cm i diameter. It produced two more flowers before decided that was quite enough.

Euphorbia obesa

I have a grand, old and elongated lady Euphorbia obesa that has faithfully produced flowers every summer for years now but, sadly, she’s remained an old spinster. Until now that is, when a strapping young lad appeared ready to pollinate everything in sight!

The old, yet still very fertile, Euphorbia obesa with lots of seed pods!

The male Euphorbia obesa at 13 months old, ready to enjoy life. This species has male and female flowers and without one of each there’ll be no little children. The plant is ca. 3,5-4 cm in diameter.

Another female E. obesa, also 13 months old. This one has also been visited by the male pictured above and the fruit is just starting to develop.

The same E. obesa as pictured above. One seed pod is still maturing while the first one has just popped. Popped is really quite an accurate word to use because the fruits do actually pop when mature. There are three fairly big seeds in each pod and if you don’t take care to harvest at the right moment the seeds may just escape you since they can be flung quite some distance by the force of the exploding pod. In the lower part of the picture can be seen some of the remains of the pod that popped, but the seeds probably disappeared in some pot somewhere. Maybe they’ll germinate some day…

Pseudolithos cubiformis

The next one to start flowering was Pseudolithos cubiformis at 14 months old. It is a lovely plant with very interesting flowers. It does look quite like a rock and I can well imagine it must be difficult to find in habitat. The flowers smell like rotting meat in order to attract flies. I had no flies on hand, and without them I believe it is quite difficult to pollinate these plants. If anyone knows a good method to pollinate them I’d love to hear it!

Pseudolithos cubiformis with a cluster of buds on the right. The plant is ca. 4 cm in diameter. In the lower part of the picture can be seen another cluster of buds about to develop, though they haven’t developed yet.

Pseudolithos cubiformis with one flower just opening and another about to open right behind. The flower is ca. 1,5 cm in diameter and smelled like rotten meat. These two flowers are the only ones that have developed from the large cluster seen in the image above.

I must admit I have no experience with Pseudolithos from before, so I don’t really know what this is. Based on this picture I assume the species produces male and female flowers like Euphorbia obesa, though I don’t really know whether these are male or female. The flowers are very small – probably no more than a couple of millimetres in diameter. I’d love to hear any tips or tricks to get these plants to set fruit. 

Rebutia narvaecensis ‘espinosae’

Finally, the last plant to flower so far was Rebutia narvaecensis ‘espinosae’ at 14 months old. The name ‘espinosae’ was never validly published according to Pilbeam (1997), so the label should perhaps just read Rebutia narvaecensis – though according to a recent molecular phylogenetic study by Ritz et al. (2007) it should probably be called Aylostera narvaecensis instead. In any case, I’ve sown regular R. narvaecensis too, so I won’t be changing labels quite until I see whether there are some notable differences between them.

Rebutia narvaecensis ‘espinosae’ with their very pretty flowers. It tentatively began with this one flower,  but it seems it thought the whole thing rather enjoyable and is now setting several more buds.

The same Rebutia narvaecensis ‘espinosae’ from a slightly different angle showing the flower tube and the plant more clearly. The flower is ca. 2 cm wide, while the plant is probably about 2,5 cm wide.


Donati, D. & Zanovello, C. 2005. Knowing, understanding, growing Turbinicarpus – Rapicactus. Cactus Trentino Südtirol, Trento, 254 p.

Hunt, D. (ed.), Taylor, N., Charles, G. 2006. The New Cactus Lexicon [Text]. dh books, Milborne Port, 374 p.

Pilbeam, J. 1997. Rebutia. Cirio Publishing Services Ltd., Southampton, 160 p.

Pilbeam, J. & Weightman, B. 2006. Ariocarpus et cetera. BCSS, Essex, 140 p.

Ritz, C.M., Martins, L., Mecklenburg, R., Goremykin, V., Hellwig, F.H. 2007. The molecular phylogeny of Rebutia (Cactaceae) and its allies demonstrates the influence of paleogeography on the evolution of South American mountain cacti. American Journal of Botany 94, 1321-1332.

Zachar, M. 2004. The Genus Turbinicarpus. Spolocnost Cactaceae etc., Bratislava, 144 p.

The Nursery (Part 7: Insecticides and fungicides)

The use of insecticides and fungicides is sometimes necessary, though keeping sanitary conditions and giving the plants all the elements and nutrients they need to thrive will generally lessen the need for these things.

Synthetic insecticides and fungicides are the most effective, but there are several natural or organic types that can be used with various degrees of success. The main reason why the natural types of insecticides and fungicides have become much more popular over the past decade or two is that the synthetic versions have become drastically more difficult for the average hobbyist to buy. Another reason is that a lot of people wish to be more environmentally friendly and reduce the use of synthetic substances.

In Norway it is practically impossible to get hold of synthetic types because the use of them is so heavily regulated. It is possible to buy some ready-made stuff on spray bottles, but this is already mixed and one little spray bottle doesn’t last long (and is expensive too). It is possible to get hold of things in other countries but bringing such substances into Norway is illegal.

Many natural forms of insecticides and fungicides work fairly well, some even very well. Still, it makes it much more difficult to combat an outbreak of e.g. red or false spider mites and the mealy bug when you don’t have access to any systemic synthetic insecticides. Personally I believe the authorities are too strict on this (I can only speak for my own country here). The amounts of insecticide needed by the hobbyist are very small, and when compared to the amounts released into the soil and rivers by professional farmers it amounts to no more than a literal drop in the ocean. The problem with pest resistance against insecticides is probably a more sensible argument for the strict laws, yet the lack of available insecticides can make life difficult for the hobbyist.


Synthetic insecticides usually work best when they act both on direct contact and systemically by being absorbed through the plant roots and spread in the plant’s sap so that sucking insects will die from ingestion. The lack of systemic action is the main problem with natural insecticides as none of them (so far as I know) work in any other way than on direct contact. With some pests direct contact is easy enough to do but in most it is not. At least it is not easy if they’re spread over a large collection or if any of the plants have spines, areoles, ribs, creases and crevices or hairs and wool, in which case there is plenty of places for the little devils to hide. In other words, when it comes to cacti natural insecticides are more difficult to apply usefully than with other plants that may be happy to only develop widely spaced leaves.

Among the many natural substances that can be used to combat insects are garlic, chilli, milk, lemon and vinegar. These can be mixed with water and sprayed directly on the plant. Some of these work better than others according to what I’ve read, and some of them may potentially harm the plant. The most popular natural insecticides are so called “soaps” or insecticidal soaps. They’re usually made up of a lot of water, some natural or essential oils, and some form of detergent. There may also be other substances present. Such soaps can be bought or made at home.

The detergent is easy of course easy to find, and it’s chief role is to break the water surface tension, thus allowing the liquid to easily coat all the plant matter and the insects themselves.

The essential oils come from various trees and plants known to have various insecticidal effects. One of the more commonly used is Neem oil from the Neem treee. It is possible to buy this essential oil and mix it yourself with detergent and maybe something like garlic juice to create a spray that will in most cases work effectively to kill insects on direct contact.

I have personally tried such soaps with various ingredients, chiefly with Neem oil, chilli and garlic, but I can’t say it had much of an effect. Spider mites that I tested it on died fairly quickly, but as mentioned above it is difficult to spray this efficiently over a large collection. There will always be some insects left that just weren’t hit by the spray.

There are also mineral soaps which work in much the same way. I have tested a mineral oil based on potassium and managed to burn several of my Gymnocalyciums with it. I didn’t even manage to kill the spider mites on them…

Organic fungicide on the left based on horsetail and nettle extracts. I’ve found it to be only somewhat effective.
A mineral soap on the right containing potassium which I’ve found to be unsuitable for cacti because several of them
have been scorched – though not all my plants were so effected.

Plants are generally more sensitive to mineral soaps but, whenever using a soap of any kind it is strongly advisable to test it first on a couple of plants and only on a small area  of said plants before spraying a whole collection.

Another alternative is to make brews with plant material containing naturally occurring poisons. One way to create such an insecticide is to buy a packet of cigarettes, break them all open and pour the tobacco into a bowl of water. Let the mixture stew for a day at least and sieve it. You’ll then have a concoction containing nicotine which is a very potent nerve poison and the basis for many modern synthetic insecticides (using neonicotenoids). Another poison is solanine, a substance occurring naturally in members of the nightshade family such as tomatoes and potatoes (in fact, eating approximately two kilograms of green tomatoes can be deadly!). Some members of the nightshade family contain dramatically higher levels of solanine than tomatoes though, and brewing a tea based on the fruits of some of these plants will allow you to create a concoction potent enough to be used as an insecticide. This is all a bit time consuming though, and in the end it’s difficult to know exactly how potent the concoctions are and whether or not they’ll be efficacious on the specific pests you wish to combat, or whether or not the plants themselves will be damaged by them.

A substance known as malathion is used in some insecticides around the world, and also occurs as the active substance in some synthetic lice cures (though at a reduced concentration). I have never tried this but I suppose it may be useful against some pests unless the amount of malathion is too small.


The main use of fungicides are to prevent little seedlings being killed off by fungi. Adult plants rarely need to be treated with a fungicide unless it is to prevent fungi attacking a wound of some sort. If one keeps very clean conditions during sowing and makes sure that no fruit remains are still attached to the seed, it’s usually not necessary with fungicide for sowing either. Sterilising the soil and seeds (if one wishes) is another way to reduce or eliminate the need for fungicides.
As with insecticides, the synthetic ones are the most effective. They are also more difficult to acquire. And similarly to insecticides, fungicides can also act systemically and/or on direct contact.
Among the organic or “natural” fungicides there are plenty to choose from, some of which will work far better than others. There are many different recipes on the Internet for creating concoctions with a fungicidal effects as well as information about natural substances that are supposed to be fungicides. A simple search will yield many results. Such things as garlic, vinegar, milk and various conservatives typically used when making jam are all cited by various people as having a fungicidal effect. 
I’ve tried all the above methods in a semi-scientific experiment I did a year ago in which I sowed seeds of a single species in pots with and without fruit remains attached, sprayed the pots with those different substances as well a synthetic fungicide and kept them all separate in plastic bags. Compared with pots in a bag that was not sprayed with anything (control pots), the experiment showed that milk was harmful (it was supposed to act as a fungicide in that it promoted growth of beneficial fungi to kill the harmful ones); vinegar and the conservative ineffective; garlic maybe had a slight effect (though it smelled terribly); organic fungicide based on plant extracts had some effect; and finally the synthetic insecticide had the best effect. The control pot wasn’t really much effected by fungi either, so it’s hard to say to what extent the above fungicides had a positive or negative effect, or no effect at all. The sample size was far too small to say anything meaningful statistically. Take it simply as an anecdote therefore.

The experiment with fungicides. It yielded some interesting information but with such
a small sampling size it is impossible to say something statistically meaningful about the results.

Some growers report that using fungicides (especially synthetic ones) have a negative impact on germination rates. Personally I have not had the same experience and for me synthetic fungicides are the way to go. Then again, keeping things squeaky clean and sterilising the soil will likely remove the need for fungicides altogether. I should also say that no matter how much you sterilise the soil or use fungicides, fungi may still spread. If you see the typical silvery white wisps of hair-like filaments spreading on the surface of the soil you should immediately remove it from any nearby pots and either spray it with some form of fungicide or add sand or grit to bury the fungi. Especially if you don’t have an effective fungicide the pot should also be placed outside of its enclosed humid atmosphere.

The Nursery (Part 6: Watering, fertiliser and other additives)

As with all things related to cacti you can make it as complicated or straight forward as you like, and there is no guarantee that overly complicating things lead to better results. On the other had, not caring about such things as the pH-level of your water or the effects of the fertiliser you use will likely have a detrimental effect on your plants.

The below paragraphs on watering is about seedlings, but the other parts of this post is just as valid for adult plants.


Watering when it comes to seedlings isn’t really as complicated as it sometimes can be when they’re all grown up. As adults they may have wildly differing requirements when it comes to watering, but at this stage they all have much the same needs. Young seedlings which have just come out of their enclosed humid atmospheres like their soil to still be constantly moist and never to dry out completely. This doesn’t mean the soil should be dripping wet other than when you water them, but rather that they grow best if there is always some moisture present in the soil. How much moisture is a matter of experience and the species in question.

Most species aren’t very demanding and at least for a beginner it’s recommended to start out with some of the easier species so as not to lose heart. I remember sowing a tray full of Ariocarpus and Pediocactus among others when I was around 13-14 years old and after being very happy to see lots of seedlings appear, it was just as disheartening and demoralising to see them all die within a month, some from fungi, some from rot and some from drying out.

Astrophytum myriostigma var. nudum at three months old. At this point the plants are grown
enough that the soil should almost dry completely out between waterings. If it does dry completely
out it is not really a problem at this point either. The more difficult species should probably be allowed
to have their soil dry out between waterings at this stage.

Generally speaking, the first three months of a seedling’s life are the most difficult. It’s at this stage they’re most at risk of fungal attacks and drying out. If you can keep them in an enclosed humid atmosphere for this entire time without any problems with fungi or too moist conditions, all the better. Often this isn’t possible though, and you may often have to remove your plants from humid conditions sooner rather than later. When this happens you are immediately risking the seedlings drying out, so extra care needs to be taken at this point to ensure that they don’t.

The same Astrophytum myriostigma var. nudum as in the above photo, now five months old.
At this stage the plants can be treated almost as adults, and the soil allowed to dry out between
every watering.

Once the plants are about three months old and/or show clear signs of more “adult” growth (i.e. spines, body shape, colouring) it’s usually time to allow the soil to dry out more between waterings. This will accustom the plants to slightly drier conditions and begin hardening them. Again, this is in many ways a matter of experience and takes a bit of time to get right. Depending on the species, how and where you grow them, and the level of experience you have, I’d say it’s better to err on the side of caution and water less rather than more. Even though most seedlings who may be rot prone in adulthood aren’t as rot prone yet, it’s still easy to over-water many species at this stage.

The four 5 cm square pots in the foreground and the one on the left at the back all contain the same Astrophytum
myriostigma var. nudum
 as in the two photos above. They are now 14 months old and ready for a new repotting only six months after their previous one. If I had given them bigger pots and more breathing room in the first repotting they would all likely be larger still than they are at this point. Notice that the variety nudum refers to plants without the characteristic white flecks all Astrophytum species have to a larger or lesser degree. It is not a 100 % stable variety though, as you can see some of them with dense flocking. The other three pots in the background are filled with regular Astrophytum myriostigma and most are densely flocked, yet still a couple have almost no flocks at all.

It’s a bit intuitive as well. When you see the soil clearly drying out or some seedlings beginning to shrink a bit, it’s time to water. And if you see that some seedlings are rotting and algae and mosses are growing freely it highly likely means too moist conditions. With a little bit of practice it isn’t too difficult to reach a happy balance. Most seedlings a also forgiving of mistakes.

Whether you water from above or below, or only spray, is a matter of choice, though small seedlings may quickly be disturbed by overhead watering. Personally I usually only spray to add a bit of moisture if I think the pots are slightly on the dry side, yet not so dry as to need a full watering, while I only water from below when it’s time to water them properly. Any excess water in the tray should be removed within an hour or two, though it’s probably best to do it right away so as not to forget all about it.

pH of the water

The pH of the soil is very important, and any major imbalances one way or another will likely stunt the growth of your plants or stop them growing altogether. Most cacti and succulents receive water by way of rain which is acidic. Usually rainwater has a pH of around 5 but, coupled with thunder clouds (which often happens in summer) the pH of rainwater can reach as low as 2-3. Tap water on the other hand may have a much higher pH value depending on where you live in the world. In Oslo, the water from my tap has a pH of around 8,5 and is bordering on being classified as “hard” water. 
What this means for the plants is that if your water is hard, it will lead to the soil eventually having a higher pH value than most cacti are happy with. Cacti (most of them, at least) seem to do best with a pH of around 5,5, which incidentally is around the level of rain water. All the growers who swear by rainwater therefore have a point. I remember the curator of the local museum where I grew up and who, together with his wife, is an avid cactus and succulent collector, only used rainwater. I didn’t quite understand why at the time, but now I do.

A bottle with pH test liquid to check the pH of the water mix I use.

Still, it’s not necessarily easy to only use rainwater, at least not for me living in an apartment. To make my water more acidic I therefore add a bit of vinegar now. The amount of vinegar will vary depending on the pH of your tap water and the amount of water you’ll use. For me I add about 3 ml of vinegar to approximately 10 litres of water. According to my (admittedly cheap) pH-testing kit this seems to yield a pH-value of around 5-6. I plan to test this on my larger collection in Kristiansand next year and see whether there is any noticeable effect.
Many cacti, particularly in Mexico, grow in or directly on limestone which is alkaline. Some growers have therefore believed that the soils of these plants should be alkaline. However, the plants only absorb water and nutrients when it rains, and the acidic rain reacts with the limestone to release nutrients from it that the plants then absorb. Once the rain has stopped and the water drained off (which happens quickly) the plants do not interact further with the soil other than to merely use it for anchorage. These species will therefore benefit just as greatly from slightly acidic water as other cacti and succulents growing naturally in less alkaline/more acidic soils. 
As an aside, anecdotal evidence from many growers suggest that seeds of several cactus species germinate better in slightly acidic conditions. E.g. Steven Brack of Mesa Garden in New Mexico has suggested that seeds of many species sown outdoors germinate best just after thunder storms when exposed to fairly acidic rain. It may certainly be the case that seeds of some species have chemical inhibitors present to prevent untimely germination and are only deactivated when more acidic water is present.


The topic of which kind of fertiliser to use (and, indeed, whether to fertilise at all) is apparently a much debated one. It seems every book and every article on cacti differs slightly in opinions. Some of it may have to do with the very different soil cacti inhabit, with some living in completely inorganic soil and others in soils consisting of mainly organic matter. Some of it may have to do with the difference in growth rates between species, where some will hardly grow at all in a year while others will race ahead. Some of it may also be down to the vary big differences in the multitude of fertiliser available on the market, and the knowledge of how they effect the plants.
It may immediately seem counter-intuitive, but it’s perfectly possible for cacti and (I assume) almost every other plant in the world to grow in e.g. completely inorganic soil or, indeed, without any soil at all. The latter method, known as hydroponic growing, can be an extremely successful way of growing plants. To grow them this way they require fertiliser to provide all the essential nutrients they need. 
Most cacti, however, are able to grow in a completely inorganic soil without the use of fertiliser. They manage this by extracting all the nutrients they need from the soil itself. In order to achieve this the soil must be made up of components containing all the stuff they need. For anyone interested in trying this method out, I advise reading an excellent guide on this called “The Stone Eaters” by Dag Panco which can be downloaded free of charge from the website of the Romanian cactus and succulent journal “Xerophilia” which is a top journal in itself:
Still, most hobbyists growing cacti and succulents won’t grow their plants in inorganic soils in which the plants must work hard on their own to get food. Many hobbyists will grow their plants in nutrient-rich composts and require less fertiliser, but even so most of us will fertilise their plants whether grown in organic based or inorganic soils. Some prefer to fertilise once in the spring and maybe once in summer, some prefer slow-release granules that will release nutrients slowly over a whole year, and other prefer to fertilise regularly throughout the growing season.

One of the three fertilisers I use (they belong to the same series).
This one is without nitrogen, but high in phosphorous and potassium.

One might think that it sounds best to just give them a lot of fertiliser and have them grow faster, but it doesn’t necessarily work that way. First of all, too much fertiliser will lead to a fairly rapid build-up of salts in the soil which, in addition to being damaging to the roots of the plant, also leads to pH-imbalances in the soil – in fact this is one of the main reasons why one should repot from time to time even if it seems like the plant doesn’t need a bigger pot. Secondly, too much fertiliser can lead to an imbalance in the level and amount of nutrients available to the plant, most common of which is too high levels of nitrogen. 
Nitrogen is a vital element for all plants and is the first letter of the N-P-K symbol on all fertilisers. Too little of it will stunt or halt growth, yet too much of it may cause abnormal growth and also root-burn. If you fertilise slow-growing cacti and succulents with too much nitrogen, they may grow abnormally and elongate, and also be more at risk of disease and pests 
Phosphorus is the second letter in the N-P-K symbol, and is perhaps most important in regulating flowering. Fertilisers with relatively more of this element are usually employed when growers wish to increase the flower yield on their plants, though I don’t know of any research on how this affects cacti specifically.
Potassium is the third letter in the N-P-K symbol and in cacti, at least, is very important for the development of spines and for strengthening the epidermis (the outer cell layer of the plant skin) which helps the plant against disease and pests. Fertilisers marketed at cacti are usually enriched in this element.
The second of the three fertilisers I use. This one has a relatively higher
amount of potassium. On the bottle you can notice how it crystallizes when
it dries. Such a build-up of salts can also occur in the soil and cause problems
for the plants if not repotted.

Apart from these, there are many other elements cacti (and most other plants) need in various quantities such as calcium, molybdenum, manganese, zinc and iron. Fertilisers containing all essential elements will usually cover the needs of cacti, although it is advisable to find a fertiliser with relatively more calcium as this is a more important element for cacti than most plants. Like potassium it helps in developing spines and strengthening the epidermis. It is also advisable to find a fertiliser containing not just all essential elements, but also all beneficial elements as classified by Arnon & Stout in 1939.

Personally I use three different liquid fertilisers at the moment. One is enriched in potassium, one in phosphorous and potassium, and one in nitrogen. The one enriched in nitrogen also contains all essential and many beneficial elements, as well as having a fairly high amount of calcium. I use all three fertilisers with almost every watering at probably a quarter of the recommended strength. I try to mix them evenly, though without knowing the exact amounts of the various elements by percentage it is difficult to say what the exact amount of nitrogen, phosphorous and potassium are in relation to each other in the final water mix. Fertilisers always give the N-P-K amount in numbers (e.g. 20-8-12) which is a measure of the amount of the different elements in the fertiliser in relation to each other. I believe my final mixture is something like 10-8-15 which I’m quite happy with, though there might ideally have been slightly more phosphorous and potassium.

The third of the three fertilisers. This one is rich in nitrogen and
also contains all essential as well as some beneficial elements.

The reason I only add fertiliser to about a quarter of the recommended amount is because most cacti and succulents are slow-growing and if fed too much will quickly grow abnormally. I have not really experimented with adding or reducing the amount of fertiliser in the mix, but it seems to work fine for me so far. Once in a while I water without any fertiliser, and then usually from above. I believe it’s a good idea to vary between watering from below and above, and watering from above once in a while also helps wash away some of the built-up salts.

Finally, with regards to fertiliser, it is important to remember that fertilising the plants can be compared to feeding in humans. A varied diet containing all the essential nutrients humans need is essential for good health, and it’s the same in plants. It need not be tremendously complicated, but one should keep in mind that plants – just as humans – can react both positively and negatively to their diet.


In addition to all the elements a plant needs, it is also possible to add e.g. enzymes, hormones, bacteria, fungi and more to regulate the plant’s metabolic system or life cycle, or the soil environment. This is a bit more complicated than fertilisers and I will readily admit that I’m certainly no expert.

Three additives containing various substances meant to stimulate plant and root growth,
promote flowering and help prevent diseases and pests. Notice the one on the left has an
Opuntia in the background – this must mean it’s good! 🙂

Together with the fertiliser I add a small amount of additives in liquid form containing enzymes, vitamins, humic acids, amino acids and essential oils that are supposed to stimulate root and plant growth, flowering and the plant’s natural defences. I don’t know their efficacy, though it seems to me there is a noticeable effect. Particularly the root stimulants I believe have led to a dramatically increased growth rate in most of my plants. I also believe the flowering stimulants have led to much earlier flowering in some species than would otherwise be normal. I have had very little trouble with disease and pests so it may be that the stimulant I add to increase the plant’s natural defences is working, though I am less certain of the efficacy of this particular stimulant.

Another root stimulant. This one contains slightly
different ingredients than the one in the picture
above. It also contains humic acids.
An additive containing fulvic acids. These are
supposed to help growth and enabling the roots to
more easily absorb nutrients.
I had never used any such additives before, but after realising how widely many of these substances are used in other parts of the horticultural industry I thought they may well be very beneficial for cacti too. Though I haven’t run any scientific tests trying to make out the respective effects of the various additives, it definitely seems as if they are helping stimulate growth. Regular watering, high temperatures and long days are all very conducive to healthy and strong growth, but it seems to me that many of the plants are growing almost too well for these additives not to have a very real effect. The images below show examples of the very well developed root systems of the seedlings.

Frailea asterioides at 13 months old. These have been grown in an inorganic soil,
so they are probably not as big as they could have been if grown in an organic-based soil.
The root systems are very well developed, though. The label is 8 cm long from tip to tip for scale.

Astrophytum capricorne var. crassispinoides cv. ‘Taiho’ at 14 months old.
The root systems are large and very well developed. These have also been grown
in an inorganic soil. The label is 8 cm long from tip to tip for scale.

Lophophora koehresii also at 14 months old. Like L. diffusa this member of the genus
does not contain hallucinogens. The tap roots are very large and very well developed.
These have also been grown in an inorganic soil and the first time they were repotted, they
were placed in a 7 cm deep pot (like the one that can be seen in the previous post) to allow
the tap root to grow larger and longer. The label is 8 cm long from tip to tip for scale.

The Nursery (Part 5: Germinate, damn you!)

Sowing cacti and succulents is hugely rewarding and for me, at least, one of the best parts of the hobby. Not only is it a dramatically cheaper way to increase your collection than buying adult plants, it also allows you to follow and study their development from tiny seedlings with just two cotyledons to their name all the way up to maturity and flowering. And there is, of course, always the chance with raising seeds that you’ll get some interesting mutants.

It’s always a good feeling when you see the first little seedlings appear after sowing, and always a disappointment when they fail to do so. Sometimes you may know what the likeliest cause of their failing to germinate is, but most often you’re left guessing. And not rarely you’re left second-guessing yourself. It’s easy to assume that you yourself must have done something wrong – which certainly may be the case – but I believe that just as often the fault may simply lie with the seeds themselves.

Seed quality

On the part of the nursery or supplier, the seed quality will be affected by such things as how old they are, how they have been stored, whether or not they have properly matured, and whether or not the parents are genetically very similar or not (i.e. inbreeding over a long period of time can yield poorer quality seeds). On the part of the expecting grower, seed quality will be affected mainly by storage.

Seeds should be kept at relatively cool temperatures in a dry atmosphere. I believe temperatures between 4-8 C is ideal, although such temperatures coupled with a dry atmosphere is not so easy to achieve. The seeds also do not like large temperature variations during storage. I have not run any experiments with storage of seeds couple with germination rates, but according to various books and scientific papers the above conditions are apparently the best way to store the seeds. Generally this will keep their viability for at least 2-3 years, though some seeds will keep for considerably longer.

One and a half weeks after sowing, 100 % germination in Pseudolithos cubiformis shows excellent seed quality.
Such high germination rates are the exception rather than the rule with seeds bought from nurseries.

The same Pseudolithos cubiformis one month after sowing.

In general, species with tiny seeds (like Strombocactus) will not keep for too long. After 12-18 months or so their viability is not great in my experience. On the other hand, species with big seeds (like Sclerocactus) tend to stay viable for a long time. I would not be surprised to see certain of these species have excellent germination rates even after five years of storage.

Anyone who has sown home-produced seeds will know that they generally germinate very well, whereas nursery-bought seeds may have anywhere from 0-100 % germination. I believe the main cause of this is the age of the seeds. In general, the sooner you sow after the seeds have matured, the better germination rates you’ll get. There are some exceptions to this though – certain species germinate better after the seeds have matured for some time (months to years).

Temperature, light and moisture

The main faults for seeds failing to germinate that can be pinned on the grower is too high or too low temperatures, too much or too little light, or too much or too little moisture.

Seeds will usually germinate best with temperatures between 18-35 C. It varies somewhat from species to species what they prefer, but in general a temperature range of 20-28 C should be ideal for most species. A variation of temperatures between day and night is also beneficial for germination. The best source of heat according to a lot of experts is bottom heating, but this is definitely not required and personally I do not have bottom heating. Temperatures above 35 C will progressively lead to reduced germination rates. Some North American genera will benefit from bigger day-night temperature variations, in particular the likes of Sclerocactus and Pediocactus.

One and a half weeks after sowing most species have started germinating, and some are more or less done.  In this tray Adenium, Plumeria and Welwitschia germinated very well. Some other species in this tray did not, such as Metasequoia and Sequoiadendron. As can be seen from the thermometer temperatures reach 35 C under the plastic lid, and while some species may find this just right to germinate quickly, others may find it too hot. I’m not certain that’s why these two species in particular did not germinate but I think it’s likely.

Some species germinate better with more light, while others seem to not really care either way. Some light is certainly needed, but seeds should be shielded from direct sunlight. Except with the tiniest of seeds I always push the seeds slightly into the soil or even cover the largest seeds with a little soil. Light is a requirement, but you certainly don’t have to provide the levels of light an adult plant needs.

Moisture needs to be high, but not too high. Some seeds will germinate even if the soil is completely saturated with water, but for most I believe this will only act as an inhibitor to germinating. The obvious problem with too little moisture is that the topmost soil of the pot can dry out and then the seeds won’t germinate. With too much moisture you risk the seeds not germinating at all, but you will also get increased algae growth and be more exposed to fungal attacks. After you’ve watered the pots, it’s a good idea to allow them to drain off any excess water by placing the pots on tissue paper or news paper for some time. To know the right level of moisture takes experience, and even with plenty of experience it’s easy to get it wrong.

What to sow in

Pots and trays are the normal types of container for sowing. Pots can generally be any size you like, but the most common sizes are 5-8 cm in diameter pots. You can use smaller or larger pots as you please, but with smaller pots you have to consider that the soil will dry out more quickly and vice versa. Personally I most often use 5 cm square pots because they fit very snugly in the trays I use to keep them in. When I started up last year I used 6-7 cm pots to sow in and I have to say that it is perhaps a better size. The larger volume of soil in these bigger and slightly deeper pots allow the seedlings more space to spread their roots and the soil does not dry out as quickly as in the smaller 5 cm pots. It certainly seemed to me that they grew faster in these larger pots than later seedlings have done in the same soil mixes and environmental conditions, but in smaller pots. Alas, I am constrained by the space available to me, and though simple logic would suggest I sow less but in bigger pots, I seem unable to follow it.

For the species that develop thick and deep tuberous roots, it might also be beneficial to sow directly in deep pots. This will allow them to develop their root systems without hitting the bottom of the pot too soon, as they’re likely to do with shallower pots. It’s not really a big problem but I think they might develop better if their roots are allowed to stretch properly. After all, for many of these species their tuber(s) may be significantly bigger than the plant body itself and they invest a considerable amount of energy developing them. Members of the genus Ariocarpus usually spend the first year or two almost solely focusing on developing their tuberous root system.

Two square 5 cm pots. The one on the right is 7 cm deep and is very suitable for
species with tuberous roots. The pots can be bought from

It is also possible to skip pots altogether and sow directly in trays. The advantage with this is, like with bigger pots, that the seedlings are afforded more lebensraum and thus likely to grow faster. The downside with trays is first of all that it is easy to keep the soil too moist once the seedlings are a few months old and starts preferring slightly less moist conditions. The increased amount of soil often leads to a much larger root system too, which may be a bonus, but when you’re short of space problems can arise once you decide to prickle the little seedlings out of the tray and into pots, only to discover that the plants have such large root systems that they all need a pot of their own. Another disadvantage with trays is that if you happen to sow seeds of species with drastically different growth rates in the same tray you may find one species completely out-competing the other. Finally, if a fungal attack occurs in a tray it will spread much faster from plant to plant than it will if your seedlings are sown in pots – then you can just remove the affected pot(s). It is a less time-consuming way of sowing though, if that is a concern. And also, if you wish to sow hundreds or thousands of seeds of the same species it is probably the best way to do so.

An enclosed atmosphere

I suppose it is possible to sow seeds without any cover and have them germinate fine, but then you’d probably have to constantly spray the surface of the soil to keep it evenly moist. By far the better solution is place the pots (or trays) in an enclosed atmosphere. This is usually accomplished by way of placing the pots in a tray and cover the tray with a sheet of plastic or glass, or a plastic roof (like the mini-greenhouses you can find in most garden centres). Another method is to place the pots inside a plastic bag or even sow directly in a glass jar that can be sealed afterwards.

A mini greenhouse on the left with sliders on the top to regulate ventilation.
On the right is a tray with lots of plastic bags with three pots in each.

For most species it is sufficient to use a tray with a plastic or glass cover. It is better if the cover is not flat because then the condensation inside the tray will often form large drops on the underside of the plastic/glass directly above the seedlings, ready to drop like a bomb and unsettle and maybe kill them. A way to know if the moisture level in the soil you have used is about right is to look at the kind of condensation that forms. If the condensation is fine the moisture levels are probably good, whereas if large drops keep forming it may be too moist. If very little condensation forms it may be that it’s slightly on the dry side.

Placing the pots in plastic bags is known as the “baggie-method”. The principal reason for using this method is that with a sealed plastic bag you can keep a humid atmosphere for months or years. Most species of cacti and succulents don’t need this, but some of the slowest growing cacti can benefit from this method. In particular the genera Aztekium, Blossfeldia, and Strombocactus are very slow growing from seed (and Aztekium ritteri may be the slowest growing cacti of all), and since they grow better during the seedling stage with constant high moisture levels the “baggie-method” is the easiest way to achieve this. Using plastic bags is also a way to keep pots with and without fungal attacks separate from each other. If you’re only sowing a few species it is also a way to keep them without needing a whole tray to put them in. I use standard zip-lock bags that are just big enough to fit three 5 cm square pots.

The “baggie-method” with pots inside a plastic bag. If you manage to stay clear
of fungi and algae, the pots can stay in the bag for a year or more (if desirable).

Depending on the species the seedlings may enjoy such humid conditions for weeks, months or even years, but sometimes they want to breath fresh air very soon after germinating. Which species prefers what comes somewhat with experience, but in general I have found that the bigger-seeded the species the shorter time it likes to stay in an enclosed atmosphere, and the other way round the smaller the seeds. It is a rule with exceptions though! Genera such as Astrophytum and Frailea have big seeds, but have no trouble staying inside an enclosed atmosphere for weeks. If the seedlings start dying it is usually a clear sign that it’s high time to let them out. Otherwise I’d aim at letting them out once they’ve grown a good bit – again this comes with experience, but usually I start exposing them to fresh air after a month or maybe two in some cases. Keep in mind that even the closest kept bag (and certainly the mini-greenhouses) let out some air – they’re not exactly hermetically sealed. When it’s time to start exposing the seedlings to fresh and drier air, it should be done in stages. If they are moved straight from a very humid atmosphere straight into open and dry conditions they may have their growth severely checked by the shock. Exposing them slowly over a period of days or weeks is the way to go.

One month after sowing these Adenium, Plumeria and Welwitschia were removed from
the enclosed atmosphere and exposed to natural air and humidity levels.
They had been gradually exposed to “outside” air for about a week before they were completely
removed from the mini-greenhouse so as not to shock them.

What’s that growing in my pot?

Fungal attacks and algae growth happens to everyone, though it’s possible to avoid both. The less clean your conditions are during sowing and the more humid the atmosphere the pots are kept in, the more likely it is that your pots will be visited by all manner of fungi and algae. The main danger of the two is clearly fungi, as a fungal attack can easily wipe out every seedling in a pot in a matter of days. Algae are not immediately as dangerous, but some types will cover the entire soil surface – seedlings included – and slowly suffocate or starve them (at least that’s what I believe happens). If your seedlings grow fast enough they are likely to out-compete the algae, but for species such as Blossfeldia this is not likely.
Ariocarpus retusus have germinated well 11 days after sowing but, as can be seen in
the top part of the pot algae have started growing already. At this stage the algae are
not really a problem though. 

Apart from using fungicide to kill the fungi, the best way to treat pots heavily affected by either is to remove them from the enclosed atmosphere and expose them to drier air. You risk your seedlings being disgruntled and have them stop growing, but if the alternative is certain death there is little choice.

Keeping clean conditions and ensuring that the seeds are not sown with fruit remains still attached goes a long way to reducing the risk of fungal attacks.

An example of what can happen when sowing goes all wrong. The algae are quite
interesting and colourful at least. It takes some time for such an extreme case to develop though.
Nothing germinated in this pot, and after the algae started growing I allowed them to continue to
see what would happen. The image is taken three months after sowing.

To avoid the problem altogether you need to sterilise all your equipment and sowing medium and also have a tiny bit of luck. Equipment (i.e. pots and labels) can be sterilised in the microwave oven if they don’t melt, or washed with bleach or some similar disinfectant. Soil (the organic part) can be cooked in the microwave oven for at least three minutes at the highest setting, or baked in a regular oven for much longer. If baked in an oven it must not stay for too long though, or dangerous chemicals will be released in the soil by its components that are very likely to be very harmful to little seedlings. In the microwave I suppose the same can happen if it stays for too long. A possible harmful side-effect of sterilising soil this way is that with all the bacteria dead you don’t know what kind of bacteria will re-establish in the soil. It may be a beneficial bacterial flora, but it may also be that your soil is suddenly swarming with harmful bacteria. 
Ariocarpus scaphirostris one month after sowing. They are growing well and have a
healthy deep green colour. Sand (aquarium sand in this case) has been strewn on the surface
to combat the algae. Some algae may sometimes grow on the sand and colour it a bit green – particularly
if the pots are still kept in humid conditions. These algae are of no trouble – certainly not
anything remotely close to the colourful image above.

If everything is done correctly and meticulously you should in theory be able to keep your pots in a plastic bag for a year or more without any fungi or algae spreading. I’ve only attempted to do this once, a few years ago. I was not very successful, though I do not know whether I wasn’t diligent enough in the sterilising process or simply unlucky. In any case the end result was not particularly positive with tiny seedlings dropping dead within days after germinating.
Since I began sowing again last year I have not bothered to do this. Mostly because we don’t have a microwave oven, but also because it’s really only Aztekium, Blossfeldia, and Strombocactus that really benefit from staying for such a long period of time in humid conditions. Currently I have all three species plodding along in open-air conditions seven months after sowing (I removed them from a humid atmosphere after about two months because of algae growth), and while the two former genera are painfully slow to grow the latter is coming along nicely, pushing 5 mm in diameter…

Scarification and stratification

Scarification and stratification are methods to treat seeds that otherwise germinate only with much difficulty, or not at all. Scarification involves reducing the strength and impermeability of the seed coat to allow water and oxygen to reach the embryo – without which it will not germinate. In many species the seeds are designed to move through the stomach and intestines of animals and be worn down by this acidic environment. In others the seeds are designed to be mechanically worn by travelling in water and being abraded by sand and gravel. Still others may be softened or outright crack from very high or very low temperatures (usually over some length of time). Large seeds in particular often need some form of treatment, although this, again, is not a rule without many exceptions. Large seeds in terms of cacti usually means 2 mm or more in diameter. 
Stratification is a method designed to activate certain chemicals inside the seed which in turn gives the signal to the embryo to start germinating. This also involves temperature. The most common form (and to my knowledge the only one relevant to cacti) is cold stratification. With this method seeds are exposed to cold temperatures and moisture and/or natural light for certain lengths of time, sometimes with shorter and slightly warmer spells in between to mimic natural cycles of warmer and colder weather. After a certain length of time, or a certain amount of cycles, exposed to cold temperatures and moisture the seeds are ready to be exposed to warmer temperatures and more sunlight in the hope they’ll germinate. If not, they may need further treatment.
I have never tried stratification, though I know certain growers use this method when sowing Sclerocactus and Pediocactus in particular.
I have tried three different methods of scarification, two of which have been very successful. The first method, and the one I’ve tried the least, is to expose seeds to very high temperatures over a length of time. I collected some Baobab seeds (Adansonia digitata) some years ago in Tanzania, which are fairly large and have a hard seed coat. To treat these I boiled water and immediately after the water began boiling I poured it in a bowl an placed the seeds in the water. I let them stay in it for 12 hours and sowed immediately afterwards. With this method for Baobab seeds I generally have a 70-90 % germination rate, though I should mention that I’ve never tried sowing these seeds without treating them.
The second method I’ve tried is to soak seeds in a mixture of water and bleach (probably around 50:50 or 60:40 with least bleach). I have tried different lengths of time, from 3-15 minutes, but I can’t say I’ve seen any noticeable results. I suspect some seeds will have germinated better while others will have been unaffected, and some will probably have died from the treatment. I think it’s difficult to get the amount of bleach right (or any other acid you may decide upon). The correct amount to mix with water and particularly for how long to soak the seeds must surely vary from species to species, so I think this method may be more useful as a way to disinfect seeds (but then soaking them for only a very short time).
The third method I’ve tried is to chip part of the seed coat away using a needle. For this method to work you need good light, a steady hand, a pair of tweezers and seeds that are at least 1,5 mm in diameter (otherwise they’re just too small to work with). Basically you hold the seed with tweezers or your fingers, and press the needle down on the seed in such a way that a small part of the seed coat chips away. It takes a bit of practice and some seeds are designed in such a way that it is very difficult or impossible to find a suitable place to try and chip it. The best area to chip is slightly past the micropyle. This area is easy to find on some seeds and very difficult on others. If you can find it and chip at the right place and angle you will generally have good results, though you risk killing the embryo if you get it wrong. Personally I’ve had a lot of success using this method on Pediocactus, Sclerocactus, and the difficult Echinocactus species. I’ve had germination rates of up to 90 % with this method.

Pediocactus peeblesianus var. fickeisenii nine days after sowing (this was sown in a completely inorganic soil). This species is one of those known to be difficult to germinate but after having chipped the seeds 90 % of them have germinated. In the lower right corner can be seen the twin seed I mentioned in Part 3 of this series. Two embryos have germinated from the seed. Sadly, this seedling left for the great desert in the sky a month or so after germinating, so I don’t know whether it was a Siamese twin conjoined at the hip or whether there was actually two embryos with separate root systems. 

Another way to manually scar the seed coat is to abrade it with sandpaper or a nail file, though I haven’t personally tried this method yet. When the area of the seed coat that you’re abrading changes colour it means you’ve almost penetrated it. This should be enough for water and oxygen to penetrate the seed coat and start the germination process.

In all methods of scarification the seeds should be sown immediately. If not the seed will most likely die.


The time it takes for seeds to start germinating varies a lot from species to species. Most species will have started germinating after about 7 days, and be more or less done after 21 days. Some will begin sprouting after only two or three days, some will need two or three week before germinating, while a few may take several weeks or even months to germinate. The species that sometimes take very long to germinate generally (if not always) have large seeds. If no seeds in a particular pot has germinated after four weeks (and you’re pretty sure they should have in that time) it’s possible to remove the pot and let it dry out somewhere not exposed to sunlight, and try again to have the seeds germinate after a few months. It’s also possible to remove the seeds from the pot and store them somewhere suitable and try again to sow them at a later date.

One and a half weeks after sowing, Welwitschia is growing well.

Astrophytum asterias cv. ‘Super Kabuto’ one and a half weeks after sowing. Members of
this genus germinate readily and grow quickly.

I sowed seeds of a few species of Pediocactus, Sclerocactus and Echinocactus in 2011 that failed to germinate. The pots were left dried out on the bottom shelf in the greenhouse for almost a year before I removed the seeds. I did not store them in the best of conditions and had little hope for them when I sowed them again earlier this year. However, I did scarify them with the chipping method described above, and lo and behold 50-80 % of the seeds germinated! This not only shows how effective scarifying can be, but also the longevity of seeds.

Germination rates

Germination rates vary tremendously from genera to genera and species to species. All the important factors affecting germination rates have been described in the above paragraphs and any one of them may have a big effect. All in all I expect an average germination rate of 50 % on cacti seeds from professional nurseries. The germination rates vary wildly though. Sometimes some species will not germinate at all while a related species will pop up eagerly in the neighbouring pot.

A tray (mostly) full of Lithops one month after sowing. I’d never sown seeds of this genus before, but they germinated very well. As with most Mesembs the seeds are very tiny, and it seems it remains true with both Mesembs and cacti that species with small seeds usually germinate readily.

Lithops leslei germinating well one and a half weeks after sowing.

The same Lithops leslei as in the image above, only now a month old. They grow
fairly rapidly. The sand is added to prevent spread of both algae and fungi. At this
point the pots are no longer in an enclosed humid atmosphere.

Members of the cactus subfamily Opuntioideae often have low germination rates and take long to germinate. Columnar cacti I have little experience sowing so I will not comment on them. Most globular cacti germinate well but, again, the bigger-seeded species tend to germinate with some difficulty.

Almost all species will germinate better the fresher the seeds are. Seeds from a few species sometimes need a maturation period though – I believe these to mainly be part of the Opuntioideae subfamily.

That’s it for the germination bit. All in all it’s not a terribly difficult business. Some species are very challenging but most are fairly easy from seed. It takes a bit of practice to get it all right but it’s perfectly possible to start with a few seeds and sow them in a coffee mug placed on the window sill. As with most things it can be as complicated or simple as you want it to be. In any case it’s a lot of fun!

The Nursery (Part 4: Soil for sowing)

Which soil to use is a very large topic, and in this post I will mainly discuss soil in terms of sowing. I will, however, do a post fairly soon going into more detail about various soil components and soil types for growing cacti after the seedling stage.

Cacti seeds in general do not need any particular soil or compost to germinate, but it is wise to plan ahead a bit. After all, most cacti seedlings grow fairly slowly, and depending on how fast you grow them (and also the species) they may stay in the soil you sow them in for several months to several years. Thus it is helpful for the seedlings if the soil is of a good quality.

Soils for sowing and for general growing too, can be either organic based or completely inorganic. When it comes to sowing it is important that the seedlings never dry out completely and it’s perhaps easiest to achieve this with an organic based soil. How much organic matter to use is a matter of preference, though personally I never use more than 50 % organic matter in any soil (unless it’s required by some particular species).

The remaining parts by volume of such an organic based soil should be made up of material that will help drainage and aeration of the soil. These are both very important factors for the successful growing of cacti and succulents. To the organic matter should therefore be added sand/grit/perlite or similar substances. It is not particularly important to choose one thing or another – the main objective is to make the soil well-drained and well-aerated. Personally I like to add material like perlite and/or pumice which are light-weight, helps aeration and drainage, and also retains a lot of water in its pores which are then slowly released into the soil as it dries out helping to keep an even level of moisture for a longer time.

Grain size should be between 1-5 mm, and a mix of this range will do fine. If you add say, 1/3 (medium/coarse) sand, 1/3 (fine) gravel, and 1/3 perlite to the organic matter you should get a good well-drained soil that is light, loose, and not too coarse. It is not critical to use the specific materials above in the specific amounts. You could easily use only perlite or fine gravel, or coarse sand to add to the organic matter. If you have access to good quality sandy loam where you live, then that is a perfectly good material to add to the organic matter. The soil is ready to use when you can grab a handful of the (dry) soil-mix, squeeze it in your hand and have it crumble easily apart as you open your hand. If it does not crumble easily, simply add more drainage material.

Organic based soil with coir. The white particles are perlite (ca. 3-5 mm wide).

If you don’t want to make a soil-mix of your own, it is certainly possible to use the kind of ready made cactus sowing/growing mix you find in flower stores. Depending on where you live these may be of a good quality or a very poor one. In Norway, at least, they mainly contain peat (sphagnum moss) and some sand, as well as sometimes a little bit of perlite. Seeds will germinate just fine in this, and many species will grow fine in it too. However, personally I moved away from using peat a few years ago. I’ve never been a fan of it but in Norway it is difficult to find suitable alternatives. Leaf mold or composts are not usually sold in flower stores (on account of peat being cheaper to produce and hence more profitable). Some nurseries and garden centres do still produce and sell composts, so it’s not impossible to get hold of, but one has to work a bit to find them.

There are many reasons why I dislike peat. It is a magnet for the little black sciara fly which lays eggs in it that develop into larvae that then eat into the roots and flesh of the plants causing rot and subsequent plant death. It takes a long time to dry out completely, and is almost impossible to re-wet once it has done so – the first of which is a problem for a great number of species, while the second is obviously a problem when you want to water the plant again (particularly after the long winter rest). It also breaks down fairly quickly and in doing so it becomes compacted and squeezes air out of the soil, which is a problem for cacti. Peat has a tendency to cling tightly to the roots, so when it comes to repotting it is difficult to remove all the peat without damaging the (often) tender roots. The companies making the peat-based products often add nitrogen-rich fertiliser as well, which is a problem not just because you don’t want your cacti to be given too much fertiliser, but especially because too much nitrogen will quickly lead to abnormal growth and/or root burn in cacti.

Having said that, most cacti will grow acceptably well in a peat based soil so long as you make sure to add plenty of grit, sand, perlite or something similar that will keep the soil from becoming too compacted and allow good drainage and aeration. Be prepared to lose plants unexpectedly though!

For my part I have gone over to using coir instead of peat as the organic component of my potting mix. Coir is the hairs from the husks of coconuts, and a by-product of the coconut industry. It’s inert and contains next to no nutrients, so fertilising is required. It fairly quickly dries out in a pot and is easily re-wetted. This also means it is not a magnet for sciara flies like peat. It does often come already fertilised though, so that is something to be aware of. It does not compact the way peat does or cling to the roots. As an important aside, coir is an environmentally friendly product bringing income to many poor people in developing countries, whereas peat is not. The excavation of peat leads to the destruction of bogs which are an important habitat for a great number of plants, animals and insects, is non-renewable (short-term), and also leads to increased CO2-emissions. I will not advise anyone to use peat if it’s at all possible to use other growing material.

Though I like coir, if I can find a good supplier of high quality compost or leaf mold in the future I will probably switch to that. Being inert, coir does have certain advantages, but for species who enjoy a good bit of organic content in their growing medium I think a good compost or leaf mold is preferable. The fact that using coir requires the use of fertiliser may also be a negative for some. In fact, for a sizeable collection of plants I would perhaps not recommend coir as warmly. The necessary increased use of fertiliser leads to quicker build-up of salts in the soil which in turn means that more frequent repottings are required. In a large collection this is time consuming and depending on the soil of choice, may be expensive too.

I have also sown in 100 % inorganic soil which has many benefits compared with an organic based soil, but also some drawbacks. Perhaps the biggest benefit in the short term is that an inorganic soil is not a very friendly environment for fungi which can quickly and easily decimate a pot or ten of nice and plump little seedlings. Nor does algae thrive (as well) in this environment. The biggest drawback in the short term is that it is more difficult to keep the soil from drying out completely (after you remove the pots from their moist atmospheres under plastic), which is a very important thing for the development of healthy seedlings.

100 % inorganic soil consisting of many different components (see text further down).
The white particles (perlite) is 3-5 mm wide, for scale.

In the longer term another drawback is that the seedlings grow more slowly in an inorganic soil. This may or may not be an issue, but because the soil much more easily dries out the seedlings require more frequent waterings and one has to remember to do this. However, the seedlings are much less at risk from rot in an inorganic soil, so frequent waterings are less of an issue than with organic soils. And because they are less at risk of rot this kind of soil is not a bad option at all for the more difficult species. After the seedlings I sow in inorganic soil come out of their humid enclosed atmosphere I very rarely suffer deaths from rot. Of probably more than 200 seedlings grown this way I can probably count on one hand the number of plants that have died over the previous year (including genera such as Geohintonia, Pelecyphora, Epithelantha, some rot prone Mammilarias and other difficult species).

The only exception is Sclerocactus, Pediocactus and the other particularly difficult species from the USA. But then again, they seem to die at the drop of a hat no matter what you do. Still, I believe those genera are certainly prime candidates for sowing in 100 % inorganic soil.

The inorganic soil I use is a mixture of sand, gravel, perlite, vermiculite, crushed brick, clay, pumice, zeolite, volcanic gravel, expanded clay, expanded shale and diatomaceous earth. I don’t necessarily use all those things together, but I like the soil to be a mix of many different substances and for it to offer the plant all the macro and micro nutrients it needs. As with the organic soil mixture, I am doing a bit of experimenting with all this, so if you want to try an inorganic soil it is not necessary to use all the above components. Indeed, you could perfectly well use only crushed rocks of various kinds as the sowing material (obviously crushed to a fine grade, though).

That’s it for the soil part. As I mentioned at the beginning of this post, I will make another entry a little later going into more detail about soil components.

Now for discussing germination!