To be honest, I find the whole cactus family to be one big confusing blur. I know a lot of the names – Mammilaria, Ferocactus, Opuntia, Rebutia, Cephalocereus, Echinocereus, Parodia, Myrtilocactus and so forth – but telling them apart from one another is often more than I can manage. It doesn't help that the names change sometimes, further mixing up any small bits I've been able to pin down.
So for me, the cactus table at work is sort of like a huge family reunion for someone else's family – it's a big blur of individuals who all kind of look the same, more or less; at the same time, I can also tell that some of them are more closely related to each other than others. There are far too many of them to be able to meet them all, so I just greet everybody with a hearty cry of, "Heyyyy . . . uh, you. Guy," and hope that's good enough.
The exceptions are relatively few and far, but Cereus peruvianus is one. If that is, in fact, its real name (something I'm also confused about), and if I've identified it correctly (if I got it wrong, it's not for lack of trying; I've looked at so many pictures of bluish, columnar cacti with reddish spines that were all identified differently that I eventually despaired of ever getting a species ID and instead just wanted to get the right genus. Which I think I did.).
I bought these two guys in late February of 2004. They were, at that time, 17 inches (43 cm) tall, and that includes the height of the gallon pots they came in. They are now tall enough that they can look me in the eye: I think the last time I measured, they were five feet five inches (1.65 m), and that's been long enough ago that I know they've grown some since.
I liked them so well that I bought more, almost exactly a year ago:
These were at K-Mart, three to a pot, and I bought them and separated them and then spent many months trying to get the mealybugs off of them. 1 I'm not sure whether this has been successful or not; so far, every time I think I've gotten them all, I've wound up finding more soon after. Though it has been a couple months, now.
They've been doing reasonably well so far, even though (as you'll notice) the smaller ones are in plastic pots. Clay would be better, but I'm not going to worry about it until they need to be repotted: they're doing fine where they are, and they've been fine there for over a year, so I'll move them to clay when they tell me they want to be moved.
They will flower, though none of mine ever have. A recent customer of mine told me that she had one at home that was getting close to eight feet tall (!), that produced flowers. She was in the store because she wanted to cut it back and needed advice, though: apparently her plant is not only getting too tall for her, it's leaning badly, and when it produces flowers, the buds form next to the window it's leaning on, causing them to become deformed and never open properly. Which is a little bit tragic, for those of us who haven't been able to see it for ourselves.
The flowers are lovely, what pictures I've seen of them (I was unable to locate a public domain photo of one before this post; however, you can see some excellent pictures of unknown legal status here and here.), and it would, of course, be extraordinarily cool if one or both of mine did sometime, but I don't actually mind if they don't.
I've been surprised by customers' ideas about watering cacti. People want to know why their cactus died, and when I ask how much water they were giving it, they almost always say almost nothing at all, honest – I watered it maybe twice a year at most, or something similar. People. You do have to water cacti. Kinda regularly, even. They'll die if they get too much, but that doesn't mean you should never give them any, or that you should only water them when it rains in Tucson (unless you've accurately reproduced the Tucson climate in your living room, which I kinda doubt), or that you should only give them a teaspoon at a time.
Also. Something about cacti seems to make people want to be mean to them, generally in a way that involves glue. They glue fake flowers to them, or cartoony googly eyes, or they top off their soil with pebbles and then glue the pebbles together so that you actually can't water or repot them (which is an ongoing frustration for me personally). I understand all these practices in some way or another – gluing the pebbles together makes them easier to ship, gluing flowers and eyes makes them more attractive to impulse buyers – but, again, you're selling the plant, right? So why wouldn't you want the plant to be good quality, likely to survive, and all that? Apparently not.
Another bizarre thing people do to sell this species of cactus in particular is to claim that it's especially effective at reducing the radiation (or, in some cases, the static electricity) from cathode ray tubes. One site claimed that Cereus peruvianus is a natural negative-ion generator (read through the comments to see the specific claims). Another said that it can absorb radiation in general. A third claimed that just an extract of Cereus peruvianus would give a person "great protection" from "emission and other negative powers." This is a load of hooey, of course, on multiple levels. 2 There's actually so much accumulated hooey in these claims that it would take a whole separate post just to dismantle them, but I'll stick the short version in a (long!) footnote instead and you can read, or not read, as you like. 3
Anyway. Cacti need to be watered in general, and Cereus peruvianus in particular seems to do well if I give it a good, thorough drenching in my shower4 when the soil has gotten pretty dry, or completely dry: in practice, with the 5 ½-foot plants in the first picture, this means about every week and a half to two weeks, and for the smaller ones it's closer to every two or three weeks – I'm more conservative about them because they're in plastic, and their soil mix is also (accidentally) heavier, so I'll let them dry out, and then make them sit for another week or so before I water, just to be sure. In the winter, this slows down in both cases, due to all sorts of things (less light, colder temperatures, semi-dormancy), so it might be twice as long between waterings, but even then, they still get water from time to time, and I don't tease them with little sips.
The other necessary cactus care item is light. Indoor cacti need as much direct sun as they can get, generally speaking, but you can't actually move them out into full sun as soon as the weather warms up. They're not expecting that intensity of light, and it will bleach, scar, disfigure, or kill them to experience it all at once. Seriously. Indoor light and outdoor light are entirely different ballgames. Not even ballgames. I think one of them may be hockey.
That said, if you have enough light for them, they're not terribly difficult. Given proper care, they're also quick-growing, which is a plus for me, though it wouldn't be for everybody.
I also appreciate that they're not spiny in every direction: when I'm taking the tall ones to the shower, I kind of have to hold on to the plant itself, somewhere, lest the plant start to tip and then smash itself into a wall. With some cacti, that's not really possible, but Cereus peruvianus has relatively minor spines, in fairly avoidable spots: I can grab either side of one of the ribs between thumb and forefinger and off to the shower we go. Easy care, relatively painless, quick-growing, and - you should see these babies dance.
Photo credits: all me.
1 A lot of cactus species naturally have white, slightly fuzzy spots near the areoles (the spots where the spines emerge), which makes it really easy to miss the presence of mealybugs, especially if you've been searching for the plant in question and are all adrenalized over having finally found one. As mealybugs and cactus go together like toast and . . . something that goes really, really well with toast, it's important to check these things.
2 Actually more like a hooey split: three scoops of hooey, on top of a flim-flam cut in half, served covered in snake oil and sprinkled with bullshit.
3 The central argument here seems to be the three-part claim that: 1) Cereus peruvianus specifically, 2) absorbs radiation emitted from cathode ray tubes (the newer liquid crystal displays, and other new types of displays, don't really emit anything dangerous and are therefore irrelevant), 3) which would otherwise reach you and cause you harm.
2) is true, but it's equally true of anything else: a piece of tissue paper, a coffee mug, a can of creamed corn, a corpse – all of these also absorb radiation. 3) is debatable, but plausibly true: cathode ray tubes, especially older ones, are capable of emitting some x-rays along with light, heat, and other kinds of radiation. Whether these are produced in large enough amounts to be worth worrying about, I'm not sure (I doubt it), but the most damaging, high-energy rays aren't going to be stopped by anything short of a few inches of lead, and putting a few inches of lead between yourself and your computer monitor sort of defeats the purpose of having a monitor. 1) is plausible, but I couldn't find any actual evidence that anyone has tried to test this, and the one sort-of reference I found just said that it had been found ineffective. It's plausible because, in theory, a plant that accumulated heavy elements (lead, thallium, mercury, gold, bismuth) from the environment would be capable of blocking radiation better than nothing at all, heavy elements being, generally, better blockers of radiation right up until you get to the really heavy elements, like thorium and uranium and plutonium, which are radioactive and therefore sources of radiation. Again, though, with our hypothetical bismuth-concentrating cactus, we have the problem of trying to read your monitor through a plant.
The claim is typically that placing the cactus next to your monitor will reduce radiation, but any radiation going out the side of your monitor was never going to affect you in the first place, and anyway if you're worrying about all radiation in every direction, your best bet would be to quit screwing around and encase your monitor in concrete already. At the very least you should surround it with lots of Chinese-made toys.
4 Like I do with all of my plants except one Cordyline: it's huge on its own, and in a massive clay pot, which is huger, the combination of which makes it more or less unliftable except for extremely special occasions.