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.
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.
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.
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.