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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.