FRIDAY, JANUARY 18, 2008
Pity poor Hylocereus undatus.1 Though a perfectly interesting species in its own right, you’ll never see it when you’re looking over the plants at your local Lowe’s or supermarket or garden center or wherever you buy them, even if you’re looking directly at it. Why’s that? Because 99.99% of the time, you’re seeing this:
These brightly-colored cacti are actually two different species of cacti grafted together. The top plant in these photos is a Gymnocalycium species, often called “moon cactus,” which has mutated in such a way that it is unable (or maybe just unwilling: they seem kind of spoiled if you ask me) to produce the chlorophyll it needs to photosynthesize. These have been around for years: I remember seeing them as a little kid. The ones I remember, though, were always kind of a neon red: the pinks and yellows and oranges and purples like in the picture are a semi-new development.
The Gymnocalycium produces offsets pretty easily, even when grafted, and the offsets so produced can be grafted to a new base, perpetuating the plant, though it’s my understanding that even the best grafts only last a few years, as the base grows faster than the Gymnocalycium. After that point, the difference in speed between the two becomes too great for the graft to hold together, and the two split apart. Some of the sites I ran across in researching this one seemed to be suggesting that the Gymnocalycium, if removed from the base and replanted, will remain colored until it dies from lack of food; other sites implied that severed grafts would spontaneously begin to produce chlorophyll even though they never had previously, and could be planted on their own. My personal suspicion is that both are true: the “purple” grafts, if you look closely, do contain some green, towards the center of the plant:
So they probably could begin making food for themselves if they really needed to. Peanut butter sandwiches, at least. At the same time, the neon yellow and orange and pink give no indication of having any green pigment in them whatsoever, and so I would guess that those probably couldn’t make it on their own. We do have a few plain green Gymnocalycium at work, but they don’t do anything terribly interesting and just look like your ordinary small green beanbag-shaped cactus. A couple of them do color up a little in the summer: they stay green but have a red / purple cast to them, especially on the most exposed portions of the plants. It’s not especially attractive: mostly they just look kind of burnt.
But who cares about the Gymnocalyciums anyway, right? What we’re really interested in is the base, the sad little, put-upon, servant of a plant that’s doing all the heavy lifting.