Lithops—Living Stones Redux
Lithops, the “living stones” of South African deserts, and the succulent subject for this month, have fascinated people for centuries. There’s something about these small, stone imitators, supremely unplant-like plants, that catches the eyes even of people with little interest in plants. Almost everyone who likes to grow things will want to give them a try. Unfortunately, without an understanding of what Lithops need, these attempts almost certainly are doomed to failure, as Lithops are prime examples of what I like to think of as “counter-intuitive” plants, with needs that defy common sense. If not treated properly, the plants generally rot and will turn to mush surprisingly quickly.
Lithops is a medium-sized genus in the Aizoaceae (or by some, the Mesembryanthemaceae, the ice plant family). Growing over a considerable portion of both South Africa and Namibia, these tiny plants manage to thrive in what seem to be desolate wastelands, hot (and sometimes very cold in winter as well), sun-blasted and subject to droughts that may last as long as several years. Nearly invisible in habitat until they burst into flower, the plants combine the ability to flourish in the harshest environments with an unmatched mastery of camouflage. In their forbidding homelands Lithops survive by living mostly underground, with just the flattened tops of their tightly joined leaves staying flush or a little above the surface. Each individual Lithops consists of nothing more than a pair of fused leaves known as plant bodies, surrounding a reduced and quite invisible stem. Translucent areas at the tops of the plant bodies act as windows that allow light to filter deep into the interior of the plants. Consequently they photosynthesize from the inside, protecting themselves from desiccating heat and light. Odd as it may seem, a number of succulent plants (some related to Lithops, some not) have independently evolved light-transmitting windows, but generally these are simply areas of transparent green or gray; Lithops have taken their windows and made them into unique devices for camouflage.
The windows in various species of Lithops may cover the whole of the exposed tops of the plant bodies, but more often they assume intricate shapes, a maze of lines that hardly seem like translucent windows at all, while the tops of the plant bodies can be marked with lines and colored dots as well. These colorful patterns may imitate the immediate habitat of the plants to an astounding degree. If they are growing on a hill covered with orange-brown pebbles, the plants will be orange-brown; if the next hill has gray pebbles, the lithops there will be gray as well. As a result, small plants of Lithops can be almost completely invisible except when they display their yellow or white flowers for a few days towards the end of their growing season. Larger, multi-headed clusters, or simply larger, rain-swollen individual Lithops, are easier to see, that is if one knows enough to recognize these small objects as plants. When shrunken in dormancy, even multi-headed Lithops hunker down at or even below soil level, and, especially if covered up by blowing sand and dirt, can rather effectively seem to disappear.
As mentioned, Lithops flowers are either white or yellow, the color almost always consistent within a given species. The combination of just two basic colors of flowers and an almost unending display of plant patterns and colors has led in the past to wildly divergent ideas about what constitutes a species within the genus. The count of species of Lithops by different botanists has ranged from as many as 300 to as few as two. These days, however, most authorities agree on a total of a few dozen valid species, along with at least that many distinct varieties and forms that show almost every color and pattern imaginable, from white to yellow, from green to red, from brown to bright purple.
Besides flower type and plant pattern and color, a third, extremely unscientific, way to separate Lithops is by plant shape. In a relatively few species the gap between the plant bodies opens wide, giving a two-lobed look to the plants, while in the majority of the genus the space between the leaves is reduced to just a narrow furrow. The gap-furrowed species include Lithops divergens (and its much larger variety, amethystinum), L. helmutii, L. comptonii and the rare L. viridis. Steven Hammer, an authority on the plants, refers to speculation that some of these divergent-leafed Lithops, particularly those largely green in color, may be primitive species. In cultivation, the various gapped species have little in common, L. helmutii, for example, quickly multiplying and generally being pretty easy to grow, while L. viridis and both varieties of L. divergens clump slowly if at all and tend to be difficult in cultivation. As an aside, L. divergens var. divergens, a tiny, greenish plant from Namaqualand, even after extraordinarily heavy rains, remains very low to the ground, protruding not much more than a eighth of an inch above soil level. It was the first Lithops I saw in the wild, and the difficulty in finding it made me wonder if Lithops in general were indeed as hard to see as reported. Fortunately for me, that wasn’t the case.
A fourth way to separate out Lithops, that leads into the subject of their culture, could consist of sorting them according to the rainfall patterns of their habitat, winter or summer. Species native to the coastal regions of western South Africa and Namibia receive winter rain, those from farther east get rain in the summer, while others from various in-between localities may be rained on according to quite different climatic schedules, late summer through fall, for example. With a few exceptions, however, generally speaking the same culture will work for Lithops regardless of where their origins lie.
Carefully camouflaged and sequestered underground, these juicy, defenseless plants manage to thrive in regions where hungry insects and other animals roam incessantly in search of vegetable matter to eat. What happens, though, when they are moved to the seemingly benign environment of a flowerpot? As mentioned, Lithops flower near the end of their growing season, typically in mid-autumn. After flowering, the furrow between the plant bodies deepens and opens up, revealing a new set of plant bodies, arranged at right angles to the old ones. This is when trouble usually begins for people trying to grow Lithops, for at this moment, and for the next several months, the plants must be kept bone dry until the old plant bodies have shriveled and become literally as thin as a sheet of paper. Giving water to Lithops before the old leaves have dried totally results in the plants swelling up and choking off their emergent bodies, leading to rapid rotting and death. Holding back water until the time is right will result in the new, brilliantly marked, plant bodies bursting through the remains of last year’s growth and starting their new yearly cycle. It’s true that some Lithops can withstand water when still dormant without dying, but as a general rule (in our area, at least) it’s best to keep them completely dry. The late Lila Lillie, who first taught me about these plants years ago, used to say that she would tell her customers that if they absolutely had to, they could squeeze a drop or two of water onto a dormant Lithops from an eyedropper, explaining to me that it wouldn’t affect the plant at all, and would make the human feel better, but total dryness is best. With multi-headed plants some of the old plant bodies may not all be absorbed at the same rate. It usually won’t hurt to wait until they all have shriveled, but at times I’ve lightly watered just one side of the plant with satisfactory results. The most dramatic way (other than sudden death) that the yearly transition can go wrong is what is called “stacking.” In this the new growth pokes out long before the old plant bodies have shriveled, giving the appearance of one lithops sitting directly on top of another one. This can call for drastic measures, and a little surgery can help, cutting away the old, still turgid leaves and leaving their cut ends to dry and behave more acceptably. This generally works, though not always.
A large number of Lithops species grow in winter rainfall areas, but only a few, such as the beautiful, completely pink-purple Lithops optica fm. rubra, absolutely won’t diverge from their built-in calendar and insist on growing in late summer right through winter. Typically, though, a Lithops will be ready for watering around late April or May and will finish its growing cycle in late October or November, when the plants begin to split. Even when they’re growing Lithops don’t need to be watered too often; every ten days to two weeks is generally plenty. Some growers give them less water than that, particularly in mid-summer, and though it won’t hurt them much to go without water for longer than usual, it’s always a good idea to water them thoroughly when water is given, in order to create good root growth. By the Bay, they should always get as much light as it is possible to give them, inland and over the hills, a little shade might not be a bad idea.. Although they grow mostly buried in the soil in habitat, trying to duplicate that will generally lead to their rotting in our region of much greater humidity: the plant bodies should be raised up well above soil level. A soil that is low in organic matter is best, but the plants aren’t terribly fussy about what they’re growing in as long as it drains very quickly. With heavy fertilizing it’s possible to grow relatively enormous plants, but these often have a tendency to rot over winter. A few Lithops will remain permanently solitary but most will gradually cluster and form small clumps over time. In the wild these clumps are quite visible. The prettiest clump I’ve seen was a dozen or more headed plant of L. meyeri growing in quartz chips on a low saddle between hills in the Richtersveld, in far northwest South Africa. Its almost pearly, blue-white coloration closely matched the surrounding pebbles, but the plant itself, raised more than an inch above ground level and six inches across was extremely visible, that is until you turned your head away and then had to find it all over again.
Lithops grow fairly easily from seed and also hybridize very readily, but the true species and varieties usually have far better color and markings than random hybrids. These general rules of cultivation are applicable to all of them, but some species are quite hardy while others are very difficult. L. schwantesii, L. dinteri, L. divergens and L. ruschiorum can all be difficult, as can L. optica with its rigid internal calendar, and L. otzeniana as well (a shame as optica rubra, with its brilliant color, and otzeniana, with neat little raised islands of contrasting-color around its perimeter are really great plants). Perhaps using a slightly different watering schedule with some of these species might help, but many of them seem simply to be fussy and can’t handle our relatively humid climate and long, cloudy winters. On the other hand, L. lesliei, L. aucampiae, L. bromfeldii, L. hookeri, the sometimes fabulously colored L. dorotheae, L. olivacea, L. salicola, L. pseudotruncatella and L. verruculosa are all easier than most, and, along with their numerous varieties, can provide a novice grower with all the Lithops he or she may need. I still have the first two lithops I bought, in 1972, L. lesliei and the subspecies of L. julii once called Lithops fulleri, and believe me, when I bought them I had neither good growing conditions or any knowledge about the plants at all. And if I could do it then, you can do it now!
The Garden has a good collection of Lithops, and these days we generally have some available at the plant sales, although because of their very specialized needs I don’t like to leave them on the plant deck, to be purchased without information.
