| Amethysts, Pearls and Other Things
Along with last month’s subject, Echeveria, a number of other New World members of the Crassula family have found their way into cultivation. The most prominent of these are the couple of dozen, almost exclusively Mexican, species of Graptopetalum, Pachyphytum and Sedum. S everal additional genera of New World Crassulaceae include interesting and worthwhile plants as well. Some of these are widely cultivated horticultural subjects, others, less common, have been valued by generations of growers of succulents, and some have remained quite rare, almost unknown outside their habitat and a few botanic gardens and choice collections.
Typical Graptopetalum and Pachyphytum have succulent stems ranging from a quarter to a half inch thick, surmounted by fairly loosely arranged rosettes of succulent leaves and generally resembling a long-stemmed echeveria such as Echeveria multicaulis. In either genus the leaves may be angular or more-or-less elliptical. The best way to tell the two genera apart is by their flowers. Graptopetalum flowers look like open, five pointed stars, usually in pale colors of tan or light yellow. Their flowers resemble those of Sedum, the ancestral genus of all the New World Crassulaceae. In contrast, Pachyphytum have bell or tube-shaped flowers, crowded along an arching stalk.
Graptopetalum paraguayense, undoubtedly the most common of these plants in cultivation, is a mainstay of succulent dish gardens the world over. Its stems gradually elongate and curve while its thick, angular-pointed, flattened leaves make a loose rosette at the stem-tips. When given adequate light, the leaves develop a thick white or even slightly pink or purple waxy coating, although plants that resemble G. paraguayense with a great deal of leaf color usually are hybrids. Stems cuttings propagate readily, and leaf cuttings produce new plants almost as easily though more slowly. Oddly enough, the habitat of this extremely common plant, in cultivation for centuries, was unknown until quite recently. It turns out that G. paraguayense is a highly endemic species, restricted in nature to a single mountain in northeast Mexico that rises abruptly out of a low plain covered with tick- and snake-infested scrub forest.
Although Graptopetalum goldii somewhat resembles a smaller, much slower growing G. paraguayense with pale turquoise, spoon shaped leaves, most other members of the genus form short stemmed rosettes that either cluster densely from the base or grow from wiry, six or eight inch subsidiary stems. G. macdougallii, with long, thin turquoise leaves, will happily start growing in any pot within reach of its runners. The clustering graptopetalums also include G. rusbyi, from southern Arizona. Many of these plants are pretty nondescript but a few are very attractive. G. filiferum, resembling a two inch stylized gray sunburst, has been hybridized with echeverias to produce beautiful little plants with evocative names such as Graptoveria ‘Silver Star’. The somewhat similar G. bellum (originally called Tacitus bellus), discovered not that long ago in the state of Durango in northwest Mexico, also makes clumps of very flat, extremely tight little rosettes crowded with grayish-silver leaves. In contrast to its drab-flowered relatives, the flowers of G. bellum look like brilliant red stars on display around the end of the year. The thick, elliptical, pale amethyst-colored leaves of G. amethystinum, distributed along a very slow-growing succulent stem, have made it a treasured species for generations of growers.
Except for color, Pachyphytum oviferum, with pale blue-white leaves shaped almost like eggs, resembles G. amethystinum quite closely, and shares the slow growth of the other plant as well. Pachyphytum as a genus display less range of form than does Graptopetalum. Some have leaves rather sparsely distributed along their succulent stems and some bear more definite rosettes of leaves. The stems themselves elongate fairly rapidly in some species; others remain almost stemless for many years. Many have leaves that range from blue-white to quite intense blue (such as P. coeruleum), but the non-glaucous (unpowdered) leaves of the uncommon P. viride turn red with adequate light while P. werdermannii has almost pure white leaves that may flush pink or purple. P. glutinicaule is easily identifiable by its sticky stems, while species such as P. compactum and P. coeruleum have sharply faceted leaves that resemble mineral crystals instead of the organic ovals and ellipses of the other species. P. hookeri, another slow growing species, has small blue leaves the shape of breasts, closely enough to engender peculiar comments at times. P. longifolium, a less commonly cultivated plant, can become fairly large, with an erect stem almost two feet tall, topped by thick, somewhat spindle-shaped leaves which make a sparse rosette. Growing on steep, rocky slopes, as is the case with most pachyphytums, P. longifolium, found in Hidalgo State in central Mexico, lives along crumbling limestone cliffs. P. oviferum requires more warmth than most species, and although popular in cultivation for a very long time, also is a plant with an extremely limited range in the wild. When pachyphytums flower, the contrast of their pale blue-white outer sepals with their bright orange to red petals further adds to their appeal. As indicated, there are many hybrids plants in this group. Pachyveria and Graptoveria are bigeneric genera, Pachyphytum and Graptopetalum crossed with Echeveria. Sedeveria is another bigeneric cross, this time Echeveria by Sedum.
The genus Sedum itself contains a great number of plants from all the continents of the northern hemisphere, although some groups of related species are gradually being split off into new genera. Mexico is home to well over a hundred different sedums, most of them rather uninteresting, often rapidly spreading plants with succulent leaves that make good ground covers in areas where the temperatures don’t drop too low. Among the very well known Mexican plants, the “donkey’s tail,” Sedum morganianum, its long, pendent stems densely cloaked with pale green leaves, probably is the most popular in cultivation. If happy and given a fair amount of shade, a soil mix with a good deal of organic manner and protection from frost, from time to time it may produce its velvety crimson-purple flowers at the ends of its branches. The “Mexican Jelly Bean,” S. rubrotinctum, with elliptical succulent leaves that color up bright red in good light also has been widely grown for many decades. Similar species, but a bit more uncommon, include S. stahlii, with leaves geometrically arranged along its stems, S. lucidum, with larger, wider, shiny, almost semi-circular leaves, and S. hernandezii, described fairly recently, a more robust, upright growing plant otherwise quite similar to S. rubrotinctum. S. burrito, also comparatively new to cultivation, resembles a slightly less elongated, more delicate version of the standard “donkey’s tail.” Sedumpalmeri, a good plant for rock gardens, forms medium sized rosettes and sends out big sprays of yellow flowers, while S. hintonii (formerly called S. hystrix), with small rosettes of turquoise leaves densely covered with short hair and still quite rare in cultivation, requires more shade, protection from frost and somewhat careful watering.
The most interesting Mexican sedums, however, probably permanently rare in cultivation, have a growth form like a little tree, and make fine natural bonsai. A number of them have smallish, elongated green leaves on fairly thin branches that emerge out of a fleshy, swollen trunk, often with peeling bark. These include S. oxypetalum, S. frutescens and S. quevae. Sedum torulosum looks quite different, with thick, branching, upright stems that end in small, dense, glaucous rosettes, Back in the days of freely collected plants, specimens of these species were highly coveted, but now they hardly show up at all, as it would take a great deal of time to raise one from seed or cuttings to maturity.
Thompsonella, a genus of rarely cultivated Mexican plants, deserves to be better known. The half-dozen or so species form compact, stemless rosettes that generally resemble echeverias, yet, somehow, don’t. Their leaves, often covered with purple to white powder, are perhaps thinner and more brittle, and their flowers, often very small, seem more like those of graptopetalums or sedums than echeverias. The plants occur in quite arid areas, often on limestone and at fairly low elevations. As a rule they are a little touchier in cultivation than echeverias, and don’t grow nearly as freely from leaf or bract cuttings. T. minutiflora probably is most common in cultivation, and T. platyphylla may be the most interesting.
Cremnophila is a very small genus of just two species that have migrated back and forth from Echeveria and Sedum over the years. They look rather like a pachyphytum with pale yellow flowers that in one species (C. linguifolia) resemble an echeveria and in the other (C. nutans), a sedum. They can be slightly touchy in cultivation, and their best feature is the deep chocolate brown color of their leaves when grown well.
Lenophyllum is another genus of relatively few species. The small plants more-or-less resemble sedums, with sprawling or short stems densely covered with pointed, terete little leaves, gray or brown or slightly spotted. L. guttatum is probably best known in cultivation, but lenophyllums can become pests in greenhouses, as their leaves, and especially their bracts when flowering, will detach at the slightest touch and grow into hordes of new plants. If kept outdoors in full sun and only sparsely watered they will maintain a compact appearance, but otherwise they have the properties of a succulent weed.
Villadia, with about twenty species that range from southern Texas into South America, resemble sedums, but differ in flower structure. Some become fairly large while others look almost like small club mosses. I’ve seen some of these smaller species in high altitude peat swamps in Central America, at over 11,000 feet elevation, where the ground shook like jello as I walked on it, and the plants shared their habitat with a small Puya, odd Blechnum ferns and true Lycopodium (club moss) species. It seemed a place suitable for dinosaurs to emerge from, and about as far from a desert landscape as I can imagine.
As is often the case with succulent plants, the fast-growing species of Graptopetalum, Pachyphytum and Sedum are so widely distributed that people rarely think of them as unusual or desirable plants, but many species are quite rare, both in nature and in cultivation. Most grow easily, fast or slowly depending on species, and respond well to a rapidly draining succulent mix with a decent amount of organic matter, regular (typically weekly) watering in the warm months of the year, and a drier period in winter, with watering reduced to once every two or three weeks. They generally need sun or extremely bright filtered light to maintain good color in their leaves, and the white or blue ones shouldn’t be touched or the colorful, waxy protective coating on the leaves will rub off. A little less water in fall will often promote better coloring in the plants, most of which can take some frost. The easy ones are good subjects for outdoor succulent or rock gardens, while the slower ones do better in containers, either in a sheltered spot outdoors or on a bright window sill.
The Garden has a reasonably good collection of these plants, including a number not often seen in cultivation. We always will have some of them available for purchase. |
