| Summer and Winter in southern Africa : Cotyledon and Tylecodon—part II
Once Tylecodon was separated out of Cotyledon, it seemed odd that anyone ever could have considered them members of the same genus. Though tylecodons, like cotyledons, produce succulent leaves, these leaves dry up and fall off at the end of each growing season. Unlike cotyledons, the main repository for water storage in tylecodons is the stem, or in some cases, a partly underground caudex. When in leaf some tylecodons somewhat resemble cotyledons (or even certain types of Adromischus). Out of leaf, however, often for half of the year or more, the plants, depending on species, resemble a lifeless stump, a tangle of dead branches, or a sort of dried up, gray-green onion. In less obvious but taxonomically significant matters of arrangement of the leaves on the stems, or their usually upright rather than pendent, usually dry rather than fleshy flowers, tylecodons further differentiate themselves from true cotyledons.
Still somewhat uncommon in cultivation, in nature tylecodons occur only in the winter rainfall (or more accurately, summer drought) areas of South Africa and southern Namibia . Tylecodons typically consist of succulent, sparsely branched stems, with more-or-less succulent leaves and generally upright flower stalks that grow from the branch tips. In the various species the stems range from quite large to tiny—in those species with a caudex, branches are often tiny and non-succulent. Leaves run the gamut from flattened spoon shaped, to linear, to almost completely spherical. Flowering often starts when the plants are still leafless, with the new leaves following soon afterwards, although several species bloom at the end of their growth cycle instead. Although there are close to fifty Tylecodon species currently described, for horticultural purposes it’s possible to fit tylecodons into several distinct categories.
In a class all its own, Tylecodon paniculatusis not only the largest species, it also has the widest distribution, from within fifty miles of Capetown in the south, well into southern Namibia , hundreds of miles to the north. T. paniculatus can reach six feet in height, and with its thickened main stem as much as two feet in diameter it somewhat has the look of a miniature baobab tree. Its fairly thin, spoon-shaped leaves vary in degree of succulence; in some extremely arid areas the leaves may be smaller and thinner, beaten down by their environment, while in slightly better watered places the leaves will be considerably fleshier. The plants make a few short, thick branches, and send their tall, bright red inflorescences straight up into the air at the height of the summer drought. Though full sized specimens would be impractical as container plants, even smaller ones have much the same massively imposing look. Though in the wild plants often grow in somewhat shady small canyons, in cultivation they will thrive with very bright light; with less they will become somewhat leggy and unnatural in appearance.
A second group of tylecodons consists of a number of medium-sized species that range over western South Africa and Namibia , though no single species has a territory as large as T. paniculatus. A number of these mid-sized species have stems set off by persistent extended leaf bases, called phyllopodia. Both T. wallichii (of Namaqualand and points north) and the very similar T. cacalioides (from farther east in the Little Karoo), have densely arranged, long, almost spiky phyllopodia with truncated tips. In other species the phyllopodia are less regular and often not as prominent, rounded or diamond-shaped rather than protruding.
Phyllopodia are almost entirely lacking in the widely distributed T. reticulatus, but the plant makes up for its relatively unadorned stems by retaining its dried inflorescence for many years, the mass of twiggy dried stems surmounting a main trunk as wide and thick as it is tall. Out of leaf T. reticulatus can appear more like a rounded rock topped by a leafless, angular-branched shrublet than a single plant. T. pearsonii, with almost linear leaves and a few whitish stems, marked with a pattern of phyllopodia resembling pointed fish scales, is a somewhat smaller plant, rarely exceeding six or eight inches in height. The stems of T. racemosus are similar, though larger, and its proportionately larger leaves range from near-linear to quite broad. T. hallii, from southern Namibia , has a densely branched, thickened main stem, narrow leaves, and somewhat persistent inflorescences that give the plant a messy look. Hairy leaves and stems accompany the hairy flowers of T. viridiflorus, endemic to a small section of the Richtersveld.
As might be expected, the mid-sized tylecodons with strange stems, such as T. wallichii, or other odd features, such as T. reticulatus, are very popular with succulent collectors, often being the pride of collections. Without intense light, however, they, too, tend to become leggy, and structures such as phyllopodia diminish in prominence; it’s rare to see a cultivated T. reticulatus, in particular, as thick stemmed and nearly hemispherical as they often are in the wild. A number of these species, as well as T. paniculatus, have earned bad reputations among the inhabitants of their homelands because of their toxic leaves and sap. Sheep and cattle that eat these plants sicken and sometimes die, and although the chance of anything happening to owners of cultivated plants seems slight, a bit of caution when repotting plants can’t hurt.
Following the large and mid-sized tylecodons, we come to small and even miniature species. Most of these small plants are confined to the Namaqualand/Richtersveld region of northwest South Africa , the center of diversification for the genus as a whole. As well as several fairly widely cultivated (and widely misidentified) plants, a number of these smaller species are extremely scarce both in habit and in cultivation, and many are extreme endemics, native to a few small patches of ground or a few gorges in a single mountain. Their combination of localized habitat, small size, and cryptic appearance has created a still continuing story of many new plant discoveries among this group of tylecodons.
Some of the small species, such as T. schaeferianus, from the coastal areas, make masses of sparsely branched stems only a few inches high, topped by rounded leaves (a particularly small leafed form is known in cultivation as T. sinus-alexanderii). T. buchholzianus, from farther inland, also makes masses of short, somewhat thicker stems (sometimes pendent in its variety fascicularis) with an oddly grainy surface. Its linear leaves are absent for most of the year, and in habit years can go by with no leaves produced at all. Other plants, in a complex that includes T. simils and T. bleckiae, have extremely rudimentary leaves, little more than tiny black ridges near the stem tips. With only one or two three or four inch long stems growing out of a tuberous base, the fringe-petalled T. boddlyeae grows wedged between rocks in near vertical gorges cut into the single smallish mountain where it’s found.
In contrast to the hill and canyon species, most of the truly miniature tylecodons have made homes in the arid flats of Namaqualand and the Richtersveld, home to so many strange, miniaturized succulents. T. pygmaeus lives only in the quartz fields of the Knersvlakte, a part of southern Namaqualand distinguished by small and medium sized plains where a dense scattering of quartz pebbles covers an alkaline, clay soil pretty much devoid of organic matter. Sparse rains fall only during the few months of winter, accompanied by fogs that deposit as much precipitation, but in summer the quartz fields are bleak and appear lifeless. In order to survive there, plants must be small and prepared for an underground survival during the summer drought. The few tiny zigzagging branches arise from the small caudex of T. pygmaeus, bear in turn a few thick, more-or-less heart shaped little leaves that somewhat resembles Conophytum, and which disappear during summer. Its close relatives ((including T. occultus and T. pusillus) are even smaller, rarely poking their two or three thickened, cordate, rather bristly leaves more than an inch into the air. Other species (such as the tiny T. singularis) extend farther north into southern Namibia , or east into the region known as Bushmanland (T. sulphureus), and even farther southeast into the Little Karoo.
A number of small tylecodons lack the tight growth form of these quartzfield and kloof inhabitants. Depending on species, these tylecodons typically put forth either single or multiple stems that often sprawl over the ground. Less attractive than the more compact dwarfs, these plants. including T. striatus, T. scandens and T. suffultus, haven’t made as much of a splash among growers, although some of them readily thrive in cultivation.
On the whole tylecodons aren’t too difficult to grow. As is the case with most succulents with deciduous leaves, the plants signal the end of their growing period by dropping their leaves, and start their growing seasons when the new leaves first appear. Most of the larger, and in particular, more widely distributed plants should be give occasional water even when they are dormant in summer, perhaps once every three or four weeks. When in growth, if there is good light, water once a week is fine, but the frequency of watering should be adjusted downward in times of low light and overcast skies. Many tylecodons flower before they begin their growth, and a little water as the inflorescences develop won’t hurt most of them. Some species, however, in particular those from very restricted habitats in extremely arid places like the Richtersveld, northern Namaqualand and southern Namibia should be kept drier when dormant, and in some cases shouldn’t receive any water until growth actually begins. T. viridiflorus, for example, can rot quite easily if given water at the wrong time, and similar care should be taken with many of the true miniature species.
In the wild many tylecodons grow in places somewhat sheltered from the sun; in contrast, species such as T. wallichii and T. reticulatus grow fully exposed to the brightest light. In cultivation, however, they all will do well with extremely bright light, though once again, some of the miniature species should be given a bit of shade while dormant in imitation of their half-buried existence among the quartz-field pebbles. They should be grown in soil without too much organic material in it, and above all, they need extremely quick drainage. Surprisingly, a plant probably referable to T. torulosum (a small—though not miniature—species) has survived freezes down into the high teens at the U.C. Botanical Garden, but even though a number of species grow in areas of regular frosts, in cultivation it’s probably best to keep them fairly warm; except in the most sheltered, sunny and dry places they won’t survive long if planted outdoors.
With their wide range of sizes, their leaves that range from linear to spherical, and their stems often marked either by elongated or geometrically patterned phyllopodia or with attractively peeling bark, tylecodons possess many of the qualities most sought after by succulent plant enthusiasts. Not surprisingly, they’ve always been considered extremely desirable plants to have, and traditionally the hardest thing about growing them simply was finding them. Lately, however, they are becoming a little more common in the trade, although many undoubtedly will always remain rarities.
The Garden has quite a good collection of tylecodons and from time to time we have plants available for sale.
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