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!

The Nursery (Part 3: The seeds)

That wonderful feeling when you receive a little parcel in the post full of seed packets…is one I enjoy a bit too much. Hence, I may have overdone things a bit when it came to ordering seeds.

I ordered lots and lots of cacti seeds of various genera from Ariocarpus to Gymnocalycium and Puna to Rebutia, to Obregonia and Sclerocactus and so on. I also ordered seeds from various Mesembs, particularly Lithops and Conophytum which I had never done before, and some other succulents and even some non-succulents. It is a lot of fun to peruse seed lists and see all there is on offer. Between the nurseries mentioned here and all the other dozens and dozens out there, I’m sure one can find seeds on offer for just about any species and form ever described.

I have ordered seeds from quite a few suppliers over the years, and in 2013 I ordered seeds from six different nurseries around the world (the pictures of seeds do not necessarily correspond with the nurseries they’re placed beneath):

  • Steven Brack’s nursery Mesa Garden in the USA
    • Mesa Garden is particularly strong on North-American cacti, but have an excellent selection of most genera. They also have a very good selection of Mesembs and other succulents. A large number of the species come with locality information and collection numbers. Mesa Garden is also known to be diligent in ensuring that species with collection numbers are not crossed with specimens with different collection numbers (which not all nurseries are). They do not have an online store, but they have easy to use order forms you can e-mail them, or you can use Excel-sheets. Delivery times to Norway are usually one or two months, but can take up to three months. This is largely because they first of all are very busy but also because when ordering (from outside the U.S.) species on the CITES check-list they have to acquire a CITES certificate from the authorities to enclose with the parcel. This can take some time and is not any fault of theirs. Germination rates are usually very good.

    Seeds of the wonderfully interesting Welwitschia mirabilis of the Namib Desert.
    The wings surrounding the seed are to aid with airborne seed dispersal.
    The plant is a relic from the time of the dinosaurs and it can live for a thousand years or more.
    It is a gymnosperm and with it’s closest relatives (though close is stretching it!) being firs and pines,
    it is certainly no succulent.

    Seeds of Dioscorea hemicrypta X elephantipes.
    As with the above Welwitschia these seeds are also designed to spread by wind,
    as can be seen by the wings on each side of the seed. It is also not a succulent,
    but rather a caudiciform – plants that develop a water storage organ called a caudex
    above ground from which stems sprout.

    • Mats Winberg’s nursery SuccSeed in Sweden
      • SuccSeed is strong on South-American cacti and perhaps in particular Rebutia. A large number of the species come with locality information and collection numbers. They also sell various accessories such as pots and books. Their website is very good and easy to order from. Delivery times to Norway are very good, and usually the parcel arrives in a week. Germination rates are usually very good.

      Seeds of Pediocactus peeblesianus var. fickeisenii (ca. 2-3 mm wide).
      The seeds are large and difficult to germinate without some form of treatment.
      Directly below the label can be seen a “double” seed. I have never seen anything like it before.
      I originally wrote under this picture that only one seedling germinated from the twin seed, but after
      looking at some pictures taken shortly after I sowed the seeds I realised I had got this species mixed
      up with another and, in fact, two plants sprouted from it. See Part 5 of this series for a picture of them.

      Seeds of Sclerocactus mesae-verdae (ca. 3 mm wide).
      Like the above Pediocactus, these two genera from the U.S. are notorious
      for being difficult to germinate and perhaps even more difficult to keep
      alive for any meaningful length of time. Still, with mechanical scarification
      of the seeds germination was surprisingly good!

        • Ludwig Bercht’s nursery Bercht-Cactus in Holland
          • Bercht is particularly strong on South-American cacti and in particular the small globular South-American genera (Gymnocalycium, Frailea, Rebutia etc.). Most of the species come with locality information and collection numbers. They do not have an online store, but like Mesa Garden you can send an Excel-sheet. Delivery times to Norway are very good and usually takes around three weeks. Germination rates are usually very good.

          Seeds of Adenium arabicum.
          In addition to the above, I also sowed seeds of A. obesum and A. multiflorum.
          The latter began flowering one year after sowing.

          Seeds of Pseudolithos cubiformis (ca. 4 mm wide).
          This very unusual succulent comes from Somalia, and in a way it looks perhaps
          more like a living rock than any Ariocarpus or Lithops.

            • Jörg and Brigitte Piltz’s nursery Kakteen-Piltz in Germany
              • Piltz have a wide selection of genera with many interesting species. Not as many species come with locality information and collection numbers as the first three nurseries. They have an online order form you can use, or you can also send an order form on e-mail. Delivery times to Norway are very good and usually takes around three weeks. Germinations rates are usually very good.

              Seeds of Astrophytum asterias (ca. 2-3 mm wide).
              The seeds are large but unusually with large-seeded cacti, Astrophytum species
              germinate readily – often starting to appear just three days after sowing.

              Seeds of Ariocarpus trigonus (ca. 1 mm wide).
              Ariocarpus seeds usually germinate fairly well, but I have found that they
              can often be a bit hit and miss with some pots completely devoid of life
              while in others they may pop up happily.  

                • Bettina Köhres’ nursery Köhres Kakteen in Germany
                  • Köhres also have a large selection of genera, and are quite strong on Astrophytum and Lophophora among others. They also have a large and varied selection of succulents, caudiciforms and various other interesting trees and plants. Not as many species come with locality information and collection numbers as the first three nurseries. They have an online store you can use, though it is not as good as SuccSeed’s. Delivery times to Norway are very good and usually takes around three weeks. Germination rates have been a bit hit and miss for me, but generally lower than the previous four nurseries.

                  Seeds of Puna bonniae (ca. 3-5 mm wide).
                  This is a very attractive Argentinian species with very strange-looking seeds for the cactus family.
                  Sadly none of the seeds germinated. Members of the cactus subfamily Opuntioideae are
                  often difficult to germinate though.

                  Seeds of Tephrocactus geometricus (ca. 5-8 mm wide).
                  This is another member of the cactus subfamily Opuntioideae, also with interesting seeds.
                  It is somewhat similar to Puna bonniae pictured above, both from the same region of Argentina.
                  This species had a 50 % germination rate though, and the plants are growing happily.

                    • Kamil Prochazka’s nursery Kaktusy in the Czech Republic
                      • Kaktusy have a very wide selection of genera with usually more than one (and sometimes dozens) forms of the same species from different localitites. Very strong on the North-American genera such as Ariocarpus, but also on many of the South-American genera. They have an online store you can use, but it is not the most practical, and the site is not the easiest to navigate either. This is the only nursery on this list I had not ordered from before, and I may have been very unlucky, but germination rates were largely very poor. I have recently ordered from them a second time and I will update this once I receive and sow those seeds. As I have only ordered from them once, it’s difficult to comment on delivery times, but it took three and half months for the order to arrive. I don’t know if this is usual, but I believe it is common with many Czech nurseries that delivery can take several months. I think many of them are run as co-ops, so it’s possible that the delivery times are a result both of being busy, but also of having to wait for different suppliers to deliver their seeds. It is not really a problem though, as long as you are aware of it.

                      Seeds of Lophophora diffusa ssp. kubesae (ca. 1 mm wide).
                      I do not know if the subspecies is worthy of scientific recognition. I suspect it
                      is merely a regional form of L. diffusa, but I look forward to seeing how it turns out.
                      In contrast to the much better known Lophophora williamsii (Peyote), this species
                      does not contain any mind-altering alcaloids.

                      Little bags of seeds happily awaiting sowing! Seeds usually come in bags like these.
                      Sometimes labels may come with the bags, but usually there will just be a
                      catalogue number referring to the respective nursery’s seed list.

                      The Nursery (Part 2: Let there be light!)

                      Before going into detail about artificial lighting I should probably first comment on why I went with that solution instead of natural light. Most people sow using natural light, and have perfectly good success with it. I have too, of course, and I probably would have decided on natural light if I had had a greenhouse to keep the plants over winter. When I gave in to the urge to buy seeds I was living in a tiny east-facing apartment, in which there was simply no space and not enough suitable natural light for sowing cacti. And when we moved to our current apartment later that year, it was July already and suddenly a little late in the year to sow. The solution became to use artificial lighting which I had already contemplated using for quite some time.

                      I won’t go into a very detailed analysis of the various artificial lighting options in this post. Maybe I will expand on this at some later date though. There are a lot of things to consider such as the available space or how much space you need, cost of electricity, whether you want to grow the plants beyond the seedling stage, and how much money you’re willing to invest.

                      I pondered for months about what kind of artificial lighting to use. I initially did not foresee having so much space available for seed raising and planned for perhaps 0,5 m2 at most. I researched quite a bit about various options and the choice stood for a long time between fluorescent tubes or LED lights. The former was cheaper and there were several tubes on the market offering a spectrum of light simulating natural daylight. There were also tubes offering specific parts of the spectrum, such as UV, which was interesting considering UV is probably an important factor in cacti for developing the most robust spines or certain attractive grey or blue blooms on the epidermis (the outer skin layer of the plant).

                      LED was also an interesting option, though more expensive than fluorescent tubes and requiring a bit more effort to install. It has the advantage of being able to create a bespoke spectrum as it were, seeing as you can install as many diodes as you like which emit light in a specific part of the spectrum only.

                      In the end it turned out that I did have quite a bit more space available than first thought, so I decided to instead use a 400 W ballast and reflector for HPS (high-pressure sodium) and MH (metal-halide) bulbs I had bought a couple of years before to raise cacti through the winter months in Kristiansand at my father’s house. The ballast is an electrical ballast to limit the current running through the bulb as otherwise it might overload. The reflector is a relatively thin sheet of aluminium polished on the inside to a high sheen and which reflects downwards the light which the bulb emits upwards and sideways and which would obviously otherwise be of no use to the plants.

                      MH bulb with reflector.

                      HPS and MH bulbs are more efficient than fluorescent tubes and LED lights, i.e. their PPFD (photosynthetic photon flux density) output per watt is greater. The downside is that a 400 W HPS/MH bulb produces quite a lot of heat, so unless one installs a fan or two the temperature will quickly become much too high in a small or closed environment. In a spare bedroom with a window it is not much of a problem, though.

                      Generally HPS bulbs emit relatively more light in the red part of the spectrum while MH bulbs emit relatively more light in the blue part of the spectrum. For the purpose of growing plants, very simply put the former is slightly better for producing flowers and germination, while the latter is slightly better for vegetative growth. I had both kinds but I was not particularly interested in the “flowering-aspect” of the HPS bulb, and I suspected the effect of the HPS bulb on germination would be slight. I therefore went with the MH bulb and had good germination rates with it (I have not tested the HPS bulb, so I do not know if it would actually increase germination rates).

                      Not living in Kristiansand it was difficult to create ideal conditions in terms of heat, watering, and day-length, and in the end I disconnected the lamp. This time around I would able to control these parameters, however. The seeds germinated and grew so well that I quickly decided I had to expand. After all, I had bought just a few too many seeds. One bulb and one shelf would never be enough!

                      Two months after I started sowing I therefore promptly went and bought another 400 W ballast and reflector. I also bought two MH bulbs with a so-called daylight spectrum with a temperature of around 5600 K (Kelvin is in this case a measure of colour temperatures of light sources). I had no information about the spectrum on my present MH bulb and I also did not know for how long it had run (bulbs do, after all, have a limited life), so I thought it best to install two new bulbs of the same type.

                      The two reflectors hanging from the top shelf of the racks.
                      At the back on the left you can just make out an Adenium multiflorum in bloom.

                      I keep the light on for between 12-14 hours per day (I’ve landed on 12), which seems like a good amount. This may immediately sound like a lot but, after all, artificial light cannot compare with natural sunlight (unless you have a lot of it), so you have to increase the time the plants receive artificial light to make up for the reduced quality of it. I have installed electrical switches to regulate when the lights turn on and off.

                      Temperatures range between 18 C at night up to 35 C during the day (depending on the outside temperature and whether or not I keep the window wide open). For vegetative growth this range is quite ideal for most cacti, though there are some notable exceptions that prefer lower night temperatures. In terms of germination it can be on the high side considering that pots under plastic or inside plastic bags are exposed to an additional greenhouse effect. It is necessary with some additional shielding from the light as well as not placing them directly beneath the bulbs. I don’t know if the temperature has really adversely affected germination to any particular degree, though. The germination rates seem quite similar to the data I have collected on germination rates in previous years when I have sown in the spring or summer with the help of natural (shaded) sunlight and temperature variations normal in a greenhouse.

                      Now to the next part of this series: Seeds!

                      The Nursery (Part 1: Getting started)

                      In July 2013 I started up the cactus nursery in the spare bedroom. I bought two simple and open standing wood racks from IKEA with four adjustable shelves. And because IKEA are quite good at practical solutions, I could easily connect them to make one big rack.

                      This way I could hang the artificial lighting from the top shelf and have the plants at a suitable distance from the light and a comfortable height for me. It also allowed for shelf space underneath the plants for storage of various items such as labels and soil.

                      The two IKEA racks. It’s a very practical setup with the plants in a good height,
                      and with storage space underneath for various things.

                      I bought plastic trays from the plant store Plantasjen here in Norway, and initially also square plastic pots from there. These are very flimsy though, so I soon began buying square plastic pots from Kakteen-Haage which are far more sturdy and suitable. I now predominantly sow in 5 cm square pots. But for the first batch of sowing in July/August 2013 I used the other pots from Plantasjen.

                      Some of the trays were of a kind that comes with it’s own transparent plastic lid to create a mini greenhouse. I used these for the first batches of sowing, placing individual pots inside them (see image above).

                      In the middle of sowing. On the lower left is the extremely useful label maker.

                      I bought labels from both SuccSeed in Sweden and Kakteen-Haage in Germany. I also bought a Brother label maker which has become a completely essential tool for me. My handwriting is terrible, so to be able to actually print the labels was a revolution. To specify, I don’t print the white hard plastic labels themselves, but rather labels with one adhesive side to stick onto the white labels themselves. I can fit quite a lot of information on one label.

                      Closeup of a white plastic label with the printed label stuck on.
                      The plastic label is almost 80 mm long tip to tip, and 14 mm wide.
                      As you can see there is plenty of space for a printed label to contain lots of information
                       with room to spare. This label was made 04.02.14. 

                      Among the various other equipment I bought were razor blades and sharp knives for grafting, a pH measurement kit to check the water, various fertilisers and additives, different kinds of soil components, various kinds of pots, a thermometer and I’m sure some other stuff as well. Some of the above I’ll get back to in much more detail in future posts.

                      The next post will deal with artificial lighting!

                      My collection

                      I’ve always been a bit of a collector, and in my childhood I went through everything from stamps, coins, bottle tops, bullets, to rocks and shells and everything in between. I was an avid collector of all these things, but it wasn’t until I discovered cacti that I finally landed on one single hobby (though I’m certainly not averse to collecting the odd rock or fossil!). I started collecting cacti when I was around 7 years old, helped along by a plant loving father.

                      I grew up in Kristiansand, Norway, and as it happens the local natural museum and botanical garden keeps one of the largest public succulent plant collections in Norway. We would often go there and look at the cacti and other succulents when I was little, and these trips certainly inspired me to keep collecting. Of particular note they keep a magnificent specimen of Echinocactus grusonii that is at least 350 years old.

                      My collection began as a number of random species without any Latin descriptions, bought partly from local flower shops and partly grown from seed mixes bought at the same stores. A sprinkling of plants from the above mentioned museum were the only ones with proper names. At that time it was all about buying whatever I could get my hands on (which my father would fund). In no time at all our glass veranda was filled up with cacti on the window sills and in wooden beds my father made that took up most of the floor space.

                      But, as so often happens to those who fall to that succulent spell, available space has a tendency to run out. And the immediate answer is, of course, never to adjust the collection to one’s available space, but to increase the available space so that one may increase one’s collection. And so on and so forth. We (I and my plants) were lucky enough to live in a big house with a big yard, so when I was 9 years old in 1992 I got my first greenhouse. At this point my father was very much invested in the hobby himself which was definitely a good thing since he is quite knowledgeable about most sorts of plants (and had infinitely more money than me).

                      We began sowing seeds in earnest which we harvested from our own plants. The flowers were far too tempting not to pollinate, preferably with as many other flowers as possible (never mind about hybridising). It was great fun to sow about a thousand Rebutia sp. or Gymnocalycium baldianum seeds – they all germinated so very willingly! We also bought seed from the local botanical garden and from the Nordic Cactus and Succulent Society. Some of these plants are still alive and well.

                      The greenhouse soon became a size too small at around 4 m2, and only a couple of years later, in 1995, I got my second greenhouse. A size up at close to 6 m2, it was all a twelve year old boy could wish for. At this point the collection grew steadily with plants bought from various nurseries in Europe and from seed bought from Europe and the US.

                      View of greenhouse nr. 2 (1996). 

                      Another view of greenhouse nr. 2 (1997). 

                      Graciously obliging with flowers on a sunny summer day.
                      From left: Gymnocalycium horstii, Echinopsis sp., Pyrrhocactus jussieui,
                      Mammillaria guelzowiana, Gymnocalycium anisitsii

                      On parade in the garden.
                      In the back: Leuchtenbergia principis.
                      The first one on the left in the front I’m not sure about. I think it may be Echinocereus subinermis.
                      Following this one: Astrophytum capricorne, Thelocactus bicolor var. schwarzii,
                      Hamatocactus sinuatus, Astrophytum myriostigma

                      Sometimes we went on holiday to our cabin in the mountains but the cacti didn’t schedule their flowering accordingly.
                      Naturally the only option was to bring some of them along!
                      From the left: Acanthocalycium spiniflorum, an Echinopsis flower completely hiding the plant,
                      Acanthocalycium thionanthum var. glaucum, Acanthocalycium thionanthum var. brevispinum, and probably Hamatocactus hamatacanthus in the back (1996).
                      (Note the insects exploring the new and exotic flowers.)

                      Still on holiday, the Echinopsis flower seen above now with a glorious
                      Norwegian sunset in the background (1996).

                      In my late teens I began finding less and less time for the plants on account of school and parties and all the things teenagers usually like to do. Then I left my home town to go to university and for many years I would only visit my plants a few times a year. When I finished university and got my first real job (in Oslo) I suddenly found I had an acute need to fill up the windowsill with cacti. Apparently my lack of regular close contact with the plants had left me very much dissatisfied with the state of things, and a cactus-filled windowsill simply wasn’t enough. So when my wife and I bought our first apartment a year ago, I immediately saw the potential in our spare bedroom and annexed it.

                      This bedroom has now become more or less the third greenhouse (if you discount the mini greenhouse on the balcony…). Light and heat is provided by two 400 W HID bulbs. All the plants are grown from seed sown over the past 14 months, and already many of them have flowered. I am continually amazed at how quickly it is possible to grow some of these plants when given more or less optimum conditions year round.

                      In fact, they grow so quickly that I’m dangerously close to running out of space…!

                      And on that note I will end this rather long entry. The next one will be about the hundreds of tiny squatters in the spare bedroom (or so I imagine my wife sees them).

                      First entry

                      Welcome to my blog about cacti and other succulents. My wife has finally managed to convince me to start a blog about my passion, and hopefully I’ll manage to update it regularly.

                      Though I certainly find many succulents fascinating and pretty, my main interest is cacti. Cacti are succulents too, of course, though for simplicity’s sake most people just call cacti cacti, and the rest of the world’s succulents are relegated to being called, well, succulents. At least, that’s how you’ll see it written on books and journals: e.g. “Cacti and other Succulents”, “Cacti and Succulent Journal” or, indeed, in the title of this blog. It’s only when one wishes to be a bit more specific that one might refer to groups of succulents as e.g. mesembs or euphorbias. Throughout this blog, then, whenever I mention succulents, I’ll usually be referring to succulents other than cacti.

                      Living rocks, the name of this blog, is the common name for several genera of succulent plants, though two genera in particular often go by that name. Those two genera are Ariocarpus and Lithops. The former is a genus belonging to the cacti family (Cactaceae), while the latter is a succulent belonging to the mesemb family (Aizoaceae). The former is found in Mexico and Texas, while the latter is found in South Africa, Namibia and Botswana. There is also another living creature that goes by this moniker, Pyura chilensis, but as it belongs to the kingdom Animalia it will not feature here. (I encourage everyone to google the creature, though! Who needs sci-fi when you can find creatures like this right here on Earth?).

                      Ariocarpus is my favorite genus of cacti, and Lithops is one of my favorite “other” succulent genera. Thus, the name of the blog seemed very fitting. So while this blog will mainly deal with cacti, I will definitely be writing about succulents too (and maybe one or two non-succulent plants as well).

                      In addition to writing about my cacti and succulents and about my own experiences growing them, I will also write about various topics from soil composition and watering, to additives and fertilisers, to literature on succulents and more. If there is any particular topic you’d like me to write about be sure to let me know.

                      This will be it for my first post. As I have just started out on this project, the blog is naturally a bit barren, but I hope to remedy this over the coming weeks.