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.
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.
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.
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.
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.
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.
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.