I feel like a bit of a rube when it comes to Lithops spp. I don't really . . . get them. It's not that I don't understand why they are the way they are, and they're unusual, so I get why people would find them interesting. But I don't feel the interesting, personally. What I feel about them is more like a non-sophisticate in a trendy Manhattan art gallery.
"Check this one out, Ethel. It's a plant, but they made it so it looks like rocks."
"Oh my. What does it . . . mean?"
"You know, what's the artist trying to say with it. Are those supposed to be windows?!"
"Yes, George. Right there in the top. See how they're kind of translucent?"
"I'm pointing right at it."
"Look where I'm pointing. Look where I'm pointing."
"Well I'll be damned. Windows."
"So it's a plant, but it's a rock, and it's a rock, but it's a building. But it's a plant. What do you think it all means?"
"Aw, hell. I don't know about art, but I know what I like, and I don't like this. Probably just trying to say something about alienation or nucular disarmament or some garbage. Let's see if they have a gift shop."
This is, of course, my problem, not the plant's. The plant doesn't need me to understand it. And there have been other plants that I've not really seen the appeal of until I brought one home (the most dramatic example being strawberry begonias, Saxifraga stolonifera, but there have been others). So the fact that they leave me kinda cold aesthetically is of no consequence, really. I might like them if I got to know them.
But. I find them a little intimidating, mostly because I've seen several of them now just shrivel and die, more or less overnight, over nothing in particular that I could see. Not only at my present job, either: this is something that Lithops spp. just seem to do, and it's bugged me. Why? What did I do?
What I did, most likely, is I watered them when I shouldn't have. They have a more complicated yearly watering cycle than most houseplants, with two wet periods and two dry periods. The first wet period is in late spring and early summer, and the second wet period is in late summer and early fall. So one might wind up watering only in May, June, September and October, or something sort of like that, and even then you don't necessarily want to water very much. During the midsummer dormancy, you can water if they start to shrivel, but otherwise keep them dry, and in the winter dormancy, don't water at all.
A lot of customers ask about them, but then they don't buy one. Sometimes this may be because I discourage them,1 but even when I don't discourage, it doesn't usually result in a sale: they're odd, and kinda cool, but that doesn't necessarily mean that your average person is going to want one in their house, you know? I mean, David Lynch is also both odd and kinda cool,2 but I wouldn't want to buy one to take home, if someone sold David Lynches.
But I digress. At some point before I started work, someone brought in a whole bunch of them, in little 2-inch pots. I don't know how many, exactly, but we had two full 4x8 flats when I took this picture,
and we used to have more than that. So maybe three flats' worth, let's say. Whether someone got a good deal, or just got overly optimistic, I'm not sure (I wasn't there when this happened.), but it will be interesting to see how many get thrown out and how many get sold, in the end.
The biology here is interesting. Lithops spp. (and there are several species, some of which have multiple varieties, and then we get into hybrids and cultivars, so good luck identifying which particular one you've got)3 have a number of adaptations which enable them to survive an environment which you wouldn't ordinarily think of as a place likely to grow plants.
The western part of South Africa is dominated by two similar but distinct types of terrain, called Nama Karoo and Succulent Karoo. Both have very rocky, lime-rich soil and low rainfall: Nama receives between 100 and 520 mm (4 to 20 inches) of rain per year, and Succulent receives 20-290 mm (0.1 to 11 inches). If that weren't bad enough, what little water there is tends to be quickly evaporated, by hot, dry winds, perpetually clear skies (pretty much) and temperatures which are routinely above 40ºC (104ºF). What's a plant to do?
What Lithops species have done is, essentially, to jettison everything that doesn't directly assist with reproduction or water conservation. Some of these adaptations are pretty drastic when you think about it: Lithops has gotten rid of stems. (Stems!) The taproot connects directly to the leaves. The plants also often grow mostly buried, and the top of the leaves are translucent (this enables light to travel into the leaf, which is lined with photosynthetic tissue,4 permitting essentially evaporation-free light collection). They only ever have two leaves at a time (presumably, annual replacement of the leaves is their way of coping with leaf damage – which if you'd been sandblasted in a furnace for the last twelve months, you'd probably be looking to freshen up too), and offset only occasionally. They are also very slow (hence patient) plants, which can live to be 40-50 years old, or possibly over 100, depending on whose sites you're inclined to believe. Old, in any case.
Some poison would probably be helpful, since they apparently are edible,5 but I suppose camouflage is a nice alternative. It's certainly awfully effective.
My favorite bit of Lithops-related trivia that I've run across is that they are apparently known to the people in their native area by names like beeskloutjie (cattle hoof), skaappootjie (sheep hoof) and perdeklou (horse's hoof). I would never have come up with this on my own, since sheep hoof-prints aren't something I encounter in everyday life, but since I read this, I can no longer look at them without thinking of hoof-prints.
Late addition: I found a very short (3 second) time-lapse video of a flowering Lithops, which may or may not be interesting to you: link.
References: Susan Mahr, at theUniversity of Wisconsin.
South African National Biodiversity Institute 1 (Succulent Karoo) and 2 (Nama Karoo)
Photo credits: see text.
1 Which I often feel guilty about, but I don't consider them beginner plants (although many people, apparently, do). So if I know someone to be new to houseplants, I'll steer them elsewhere, just to avoid the heartbreak.
2 I think, anyway. He seems to have fallen on losery times lately, a bit.
3 This does mean, though, that you are likely to be able to find a Lithops that matches your interior décor, as long as your interior décor is mainly some kind of washed-out, low-saturation earth-toney kind of thing.
4 Other succulent species have had the same idea: many Haworthia species, including H. retusa, H. truncata, H. transclucens and several others, Senecio rowleyanus ("string of beads") and S. radicans ("string of bananas"), Peperomia graveolens, etc. The Haworthias and Senecios are both also native to Southwest Africa, which suggests that maybe there's something about that area in particular that encourages plants to evolve window-leaves. The Peperomia, though, is from Ecuador, though.
5 At least, that's the rumor. I wouldn't be inclined to test it personally. (Unless I were very, very thirsty, I guess.)