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Succulent of the Month

 
 

Very Strange Grapes

 

As I said last month, I’m going to incorporate some of my recent experiences in Namibia into some older columns. Namibia is home to a number of the most spectacular succulent plants in the world, and several of those belong to the grape family, Vitaceae. Succulent grapes fall into three general categories: vining plants, clambering plants with thickened, segmented, often angular stems, and pachycaulous caudiciforms, with enormously swollen bases either elongated into trunks or squat as egg-shaped boulders.

 

All the succulent grapes were once included in the genus Cissus, but in the 1930s a number of species were separated out into Cyphostemma, primarily because of botanically significant, but not particularly obvious, differences in flower structure. The big caudiciform members of the family belong to Cyphostemma, but far from all members of this genus are caudiciforms, or even succulents. The number of species of Cyphostemma is surprisingly large (one recent book includes about 160, another suggests up to 300), but many of them share the tropical liana morphology typical of their Cissus cousins. Similarly only a relatively few species of the widely dispersed genus Cissus are succulent plants, with most of the other species tropical vines, often with very decorative leaves.

 

The succulent species left in Cissus proper encompass both vining and clambering types, and grow in more-or-less arid regions in both Africa and Mexico . Most of the vining plants are Mexican, with annual, large-leafed vines rising from underground tubers. They’re not commonly grown in cultivation and not widely known, although several species have very pretty leaves, somewhat velvety in texture and often with white veins that contrast nicely with their glowing, emerald surfaces. Cissus tuberosus, from the northwestern Mexican state of Sonora , differs from most of its relatives because of its deeply dissected leaves, and its above-ground caudex. C. tuberosus is easy to grow, but in order to maximize the development of its caudex it needs a lean soil mix, a winter rest after its leaves fall, and careful watering when growing.

 

The clambering Cissus species, such as C. quadranglularis, have succulent stems and quickly ephemeral leaves. Though they develop thickened tuberous bases in time, their stems aren’t annual; in habitat they can cover small trees and shrubs. These species live in quite arid regions of East Africa and southern Arabia , and, not surprisingly, do best with very bright light and fairly strict winter dry periods.

 

Although Cyphostemma was separated from Cissus because of technical details of flower structure, no one would ever confuse one of the commonly grown Cyphostemma species with a Cissus. These highly succulent cyphostemmas, strictly African in origin, are prized even as young plants because of their striking caudices, often covered with peeling, papery bark. Most of these plants come from South Africa and Namibia , but other succulent cyphostemmas occur in East Africa as far north as Somalia , the home of C. betaeformis, a medium sized plant with a thick, sparsely branched pachycaulous stem that very much resembles some of the species growing thousands of miles to the south and west. A number of the East African Cyphostemma, such as C. adenocaule, have large underground tubers and send out long annual vines, while several other species, such as C. quinatum and C. hardyi, produce stems, often from tuberous roots, that, although quite succulent, lack the bizarre proportions of the most spectacular species.

 

The giant island of Madagascar , home to many rare and peculiar plants, includes a considerable number of Cyphostemma species in its flora. Many of these are vining plants, often with more or less enlarged underground tubers. In several species the enlarged parts emerge above ground, and a typical succulent Madagascan Cyphostemma consists of a long, somewhat flask shaped caudex that tapers up into an annual vine. Among the most succulent of these are species such as C. macropus and C. laza, with very large, tall caudices, while C. elephantopus has both an enormous disc-shaped underground caudex up to several feet across, and a large above ground stem as well, with a tapering shape a bit like an elephant’s tusk. Fanciers of succulent plants consider any of these cyphostemmas to be eminently desirable, but when all’s said and done, it’s the Namibian species that are still the best.

 

The most common of the Namibian species in cultivation, Cyphostemma juttae will, under ideal circumstances, reach well over six feet in height and more than two feet in diameter at the base. It produces a few upright growing branches, almost as thick as the main stem, and a compact cluster of large, tri-lobed, smooth, somewhat blue-green leaves emerges out of the growing tips every year. In the wild, in central northern Namibia , it grows in rocky places covered by thin, semi-tropical, fly-infested forest. A second species, Cyphostemma bainesii, grows considerably farther to the south, often in rocky outcrops at the base of boulders where it receives a bit a shade from the burning sun. The stems of C. bainesii resemble those of C. juttae, but the plants don’t become quite as tall, and their leaves, only about half as large, are covered with a fairly dense fuzz. There is also a plant, variously referred to as Cyphostemmaseitziana or considered synonymous with C. bainesii, that has leaves even more densely covered with silvery-white felt and a much shorter, squatter body shape, the classic forms being almost unbranched, with the look of large, ovoid eggs, two feet across, a foot and a half tall, covered with peeling, pale yellow bark. Intermediate forms exist, more branching, but still much wider than tall, with irregular caudices three feet or more wide and about eighteen inches tall; whether these are forms of C. bainesii, or seitziana, or another taxon entirely is up to the botanists to sort out.

 

In the northern parts of Namibia grow two of the most interesting Cyphostemma, both as much like living sculptures as plants. C. currorii (once known as C. cramerianus) becomes very large, as much as twenty feet tall, with a main stem five feet in diameter or more. Its trunk may bifurcate at about head level, and then re-divide into several upright, enormously thickened branches, with a few smaller branches at their tips. Its felted leaves, also tri-lobed, are very large, with segments more round in shape than the other species. All of these cyphostemmas have tan to yellow, peeling bark, but the bark of C. currorii is particularly golden in color, and the plants, frequently growing in semi-isolation near the tops of rocky hills, stand out like enormous beacons, tall, thick and golden.

 

Cyphostemmauter, with a range that extends into southwest Angola as well as northern Namibia, tends to favor arid flats or more gently sloping hillsides rather than the steeper hilltops sought out by C. currorii. It’s a large plant, too, but with a unique shape. The plants put out a main stem, up to two feet or so in height and diameter and then shoot off horizontally with a number of very thick main branches that grow almost parallel to the ground, and which put out smaller, more vertical growing secondary branches. These main branches grow in whorls, and the largest plants will have a couple of layers of these whorls of outward reaching stems. The bark of C. uter peels off in sheets like the other species, but less messily, and the plants have a smooth, almost artificial feel to them.

 

The Namibian Cyphostemma aren’t particularly hard to grow; they’re much harder to find. Even though several of them grow in the partial shade of boulders or under a thin cover provided by taller trees, they all want as much light as we can give them. During their growing season most of them respond to a reasonable amount of water, once a week or so, and when their leaves drop in fall, they should receive water much less frequently, perhaps every month to every six weeks. Their soil mix should be very quick draining, but other than that, they’re not particularly concerned with what they grow in. The form known as C. seitziana may have a very short growing season, sometimes not waking up until late June and dropping its leaves as early as late September. It sometimes grows at higher altitude than the other species (as much as 8000 feet), but not exclusively. It may do better with slightly less frequent watering when in growth (every ten days or so), and a stricter rest period after it drops its leaves.

 

Oddly enough, although most of the cyphostemmas I recently observed (in August—remember, that’s equivalent to February in the northern hemisphere) were quite dormant, almost all the plants I saw of C. uter (probably a few dozen) were starting to put out both flower and leaf buds, even though the rains weren’t due for at least four months. Other species that were growing relatively nearby were still completely dormant, with no sign of any growth at all. I’ve observed that C. uter in cultivation may keep its leaves much later than the other species, and these two observations may somehow be connected. Cyphostemma juttae can survive a certain amount of frost if dry even though it grows quite far to the north in Namibia , where extreme cold is quite unlikely. It also can withstand a good deal of water—the Botanical Garden has a plant that has survived several stints of below 20 degree temperatures and large amounts of winter rain. The plant sustained damaged from these extreme conditions, but is still alive and thriving. In theory Cyphostemmaseitziana and some of the others could also survive a certain amount of frost, but I don’t know of anyone willing to risk a plant in order to find out.

 

The East African and Madagascan Cyphostemma species require similar general care, but often will respond favorably to more water and less rigid rest periods. It seems unlikely that they would be able to tolerate as low temperatures as their Namibian relatives. The succulent Cissus species require similar care, bright light, excellent drainage, regular water when growing with a fairly strict rest period when dormant (after the leaves drop in those that have leaves).

 

All these plants will grow from cuttings (I saw a number of branches dropped from plants of both C. uter and C. currorii lying on the surface of the soil and actually sending out roots—we planted a couple of these nearby so here’s hoping they’ll survive), although not necessarily quickly. Seed propagation is somewhat difficult and slow, but once they get a start the plants will grow. If they’re placed in the ground in a greenhouse, they’ll grow surprisingly quickly, but not everyone can provide these conditions, and the plants will thrive for a very long time in suitable containers. It can be a little hard to give them enough light to prevent a degree of etiolation, but it’s possible, and occasional judicious pruning doesn’t hurt. One further note—though they’re in the grape family, and produce fruits that vaguely look like grapes, don’t eat cyphostemma fruit as it is loaded with oxalic acid.

 

Cyphostemma have always been rare and coveted. C. juttae, by far the most common in cultivation, nonetheless remains a somewhat rare plant and the rest are pretty much collector’s items, sometimes selling for surprisingly large amounts. If you see a plant, can give it the correct conditions, and are willing to spend the money, I would recommend almost any succulent Cyphostemma as an example of some of nature’s most remarkable achievements.

 

The Garden has several very nice specimens of Cyphostemma, and a number of unusual Mexican and African Cissus species as well. We occasionally have some succulent Cissus for sale, and we’ve been known to have seedlings of Cyphostemma too, so keep an eye out for them.

 

 

 

-Fred Dortort


Fred Dortort has grown cacti and succulent plants for thirty years. He's studied and observed plants in Baja California, mainland Mexico, South Africa, Namibia and the American southwest. He's lectured widely on succulent plants, has taught classes at the Botanical Garden, and written numerous articles for the Cactus and Succulent Journal, as well as publications such as Pacific Horticulture and Garden.

Fred is a Garden Volunteer. We appreciate his time and knowledge, working with the succulent and cactus collection (Arid House) and helping with propagation for our Plant Sales.

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