Conophytum, "Pebble Plants" - Cactus Club

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Conophytum, "Pebble Plants"

Plant of the Month > Species C to D

by Bruce Brethauer

   Fall is for Conophytums! Unlike many of the other cacti and succulents, which are now settling down for a period of winter dormancy, the Conophytums undergo a fall transformation which is little short of a metamorphosis. From shriveled, dry tufts of dead-looking leaves emerge miniature clusters of plump, highly succulent leaves, shortly followed by brightly colored aster-like flowers. The flowers, while being generally small, are often brightly colored in yellows, pinks, magenta and white, and are often bi- or even tri-colored with petals having whitish bases, and the flowers having bright yellow/orange centers. In some plants, the flowers are produced in such numbers that it is difficult to see the plant through the carpet of flowers. The entire transformation may take place in as little as about 2 to 3 weeks, and the daily progress of these plants as they break dormancy has to be seen to be believed.

   The Conophytums belong to the Mesembryanthemaceae, the same family of plants which includes the "Living Pebbles" (Lithops), "Tigers’ Jaws" (Faucaria), the "Babies Toes" (Fenestraria), and "Ice Plants" (Delosperma), all of which produce low mats consisting of succulent clustered leaf pairs. The Conophytums are native to western South Africa and Namibia. They are typically found in areas which are quite arid, and which receive most of its rainfall in fall and winter. As a result of the seasonal rains, these plants are genetically programmed to produce all of their growth in fall and winter, and will break dormancy in response to the shortening daylight hours in late summer. While plants in habitat may be found growing fully exposed to the sun, more frequently, Conophytums in habitat may receive partial shading from the mosses and grasses it grows with. The Conophytums typically grow in rock crevices, on very shallow pans of soil on top of bedrock, or on extremely gravely soils - all conditions in which soils are very thin, and moisture quickly evaporates. As a rule, these same habitats have very limited available nutrients; conditions which discourage the establishment of most plants. The Conophytums are able to survive in these areas because they are able to quickly absorb any available moisture, and can store moisture for extended periods. They are also able to efficiently "recycle" moisture and the minerals and nutrients contained within their tissues, and as a result, are very frugal in their need for minerals and other nutrients. The leaves of the Conophytums are extremely succulent; the leaf pairs are united together for at least part of their length; many species have leaves which are united only at their leaf bases, and produce leaf pairs with curiously shaped lobes. To my eye some of the leaf pairs are shaped like stubby pincers, others are more or less heart-shaped. Other species have leaves which are almost completely united, with only the smallest dimple or pit separating the leaf pairs. In these plants the leaves may be nearly spherical, to inverted cone shaped to almost pancake-shaped in some species. The markings of the leaves are also highly variable, depending upon the species and variety; while most species are typically of a uniform green coloration with smooth surfaces, many others are marked with darker dots, lines and textured surfaces. Like their cousins, the Lithops, some species are colored to mimic the stones in their habitats. Intense light, and cooler temperatures may increase the intensity of the coloration of some species; under the right conditions, some varieties may produce deep red, and purple pigments.

   Conophytums are small, and extremely compact plants, producing dense clusters of foliage, usually only growing to about 2 to 3 inches tall in the larger species, and are much shorter in the more compact plants. Over a period of years, plants will spread horizontally to produce dense clusters which may measure many inches across. Plants in habitat are known to spread to 2 or more feet across, but in cultivation, plants are usually maintained at smaller sizes, and are usually grown in 2 to 4-inch pots, making these plants ideal for growers with extremely limited growing space; it is possible to grow a small collection of plants on a windowsill or on a bookshelf under a fluorescent strip light.

      To grow these plants well, you must remember that these plants want to grow from fall through winter, and that they must be kept dormant and dry from spring through summer. Contrary to the way we treat most of the other plants in our collections, Conophytums should not be watered from late spring through late summer (one grower told me that he does not water his plants from Memorial day through Labor day). Beginning in early spring, water should initially be reduced, and should be withheld altogether from late spring through much of the summer: also, plants should not be fertilized at this time. Beginning in mid to late summer, plants should be given water on a more regular basis. At this time, plants should be watered well, given periodic deep watering, (allowing the soil to dry completely before watering again). Given this treatment, the developing leaves may increase remarkably in size. But here again, the grower will need to carefully observe their plants to provide adequate - but not excessive- water. If a plant is given excessive water at this time it is possible that the plant will absorb moisture until the leaves literally rupture, given too little, and the plants will produce stunted growth, and may produce fewer, or no flowers whatsoever. Properly watered, leaves will be turgid, and should produce characteristic, uniform growth, without evidence of etiolation: plants should maintain this appearance from fall through much of winter and in rare instances, into spring: if leaves shrivel during this period, it may be necessary to increase the frequency or quantity of water.

   Beginning in late winter, the roots of most species will loose the capacity to absorb moisture, and so, at this time it is advisable to reduce the frequency of water; Oftentimes, the plant will signal that it has entered into its period of dormancy when its leaves begin to shrivel, and in some species the leaves may first change somewhat in coloration.

   During their period of dormancy, Conophytums will absorb moisture and minerals from the previous year’s growth, recycling these to supply the developing leaves with scarce moisture and nutrients. Properly grown, a Conophytum will give every appearance of dying as it becomes dormant - first its leaves begin to shrivel, then they become dry, forming an envelope of dried tissue - similar to an onion skin- which protects the developing leaves which lie largely unseen underneath. At this time, the plants will have the look of clusters of dead and dried leaves, so the casual observer could be forgiven for assuming that the plant is dying or dead; but in late summer and early fall, with the arrival of rains (or renewed watering by the grower), the developing leaves enlarge, rupturing through the envelope of died leaves.

   Unfortunately, it is impossible to suggest an exact regimen of wet and dry seasons which will satisfy every species - as a rule, large leaved plants will generally tolerate more drought and longer periods of drought than the miniature species whose leaves are much smaller - these miniature species may need more frequent watering in general, and may even require periodic light watering during their period of dormancy. Trial and error along with close observation of the plants will eventually teach the grower what cycles will work best for their plants.

   In previous installments of the "Plant of the Month", I have often given the advice to move plants outdoors through the summer months to benefit from increased temperatures, light exposure and to be exposed to summer rains. If the Conophytums were subjected to this treatment, they would almost certainly perish, as they are genetically programmed to remain dormant through the summer months, and should be kept mostly, if not absolutely dry through much of this season. Water at this time of year may result in irregular development of leaves, the possibility of rot, or in a worst case scenario, the leaves may literally rupture, with the inevitable demise of the plant. If you move these plants outdoors at this time, it would be best to keep them in a position where they are sheltered from rain. I also have been told that birds have been known to pick Conophytums apart when these are moved outdoors, so in general, I do not recommend that growers move their plants outdoors unless they are completely sheltered from rains and birds.

   It is in late summer through fall that most species will produce their flowers - these are mostly smallish, brightly colored aster-like  blooms. Flowers are typically pink, magenta, yellow or white in coloration, with many plants producing attractive bi colored flowers - usually with whitish centers. In most instances, an individual plant may be in bloom for about 2 to maybe 3 weeks - growers can extend the flowering season by growing plants which flower at different periods, - in doing this, it may be possible to have a Conophytum in flower from late summer through early winter.

   In general, all Conophytums should be given bright but filtered light - many growers have had good results with plants grown under fluorescent lights (the lights should be held about 2 to 4 inches above the plants). Many species may be grown in direct sunlight, but some species may bleach or scorch when grown exposed to full sun, so I would recommend gradually exposing these plants to ever increasing light until their tolerances to sunlight can be determined. Even though many species will tolerate some shade (in habitat, many plants will grow in shaded crevices), these plants should not be grown under low light levels, as this will produce etiolated, weak growth with leaves producing rather insipid coloration. In very low light, growth will cease, and plants will eventually die. If plants are grown exclusively under artificial light sources, it is important to vary the exposure time to reflect seasonal changes in daylengtht - as the cycles of growth, dormancy and flowering are closely regulated in response to changes in the length of daylight hours. The Conophytums are very frugal in their need for fertilizers, during their growing season, they may be given a few very weak applications of fertilizer (diluted to about 1/4 to 1/6 the recommended strength). If plants are provided with a mineral rich potting medium, it may not be necessary to fertilize these plants at all. Growers generally advise that these plants be repotted infrequently - with recommendations varying from about once every 3 to 4 years (or more) depending upon the pot size and rate of growth - in habitat, plants are often found growing in very confined spaces such as crevices in rocks, so the grower should not be too concerned about plants becoming pot bound. Even though plants will produce much of their growth in winter, most species grow in regions with rather cool winter temperatures, and many species may even be subjected to hard frosts in habitat, so most of the Conophytums will tolerate cool night temperatures (to the low 40's) in the winter months - although they do not seem to suffer if they are maintained at household temperatures at this time.

   Propagation of these plants is usually accomplished by dividing the plants whenever repotting. While it is possible to establish a new plant from a single rooted leaf pair, most growers will generally divide plants into 2, 3 or 4 sections - each section containing a number of rooted leaf pairs, repotting each into its own pot. Not having divided my own plants yet, it is my understanding that the best time to divide plants is either in mid-summer, just before plants begin to break dormancy, or in mid fall, or just after the plants have flowered. Plants can also be grown from seed, which can be acquired from one of several specialist nurseries, as well as the CSSA seed exchange - but attention to detail is critical for success - seedlings are particularly prone to rot when conditions are excessively moist, and it may be some time before plants achieve flowering size -although some growers indicate that seedlings can flower in as little as a year or two. Some growers report few difficulties in growing these plants from seed - but my limited experience suggests that this is best reserved for experienced growers - the novice would be better advised to acquire established plants.

   Provided that the grower can observe the special needs of the Conophytums, they are attractive, long lived and quite distinct plants, producing attractive compact clusters of interestingly shaped, patterned, and occasionally, textured leaves. In season, these plants will produce attractive, and oftentimes, brightly colored flowers. The small size of most species will make these well suited to small spaces, and their tolerance of somewhat lower light levels makes these plants particularly suited to growing under lights. A well grown collection of these plants is a memorable sight - and some growers grow these plants exclusively. When you can find a plant for sale (these are still rather hard to come by in the trade - usually the best sources are mail-order nurseries which specialize in the so called "Mesembs") give it a try; if you have good results in growing it, chances are that you will be hooked for life on these interesting plants.

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