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.

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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.

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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.

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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.

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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! 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.