Ceropegia sp aff bosserii - Cactus Club

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Ceropegia sp aff bosserii

Plant of the Month > Species C to D

Ceropegia sp aff bosserii var razafindratsirana


by Bruce Brethauer

    The Ceropegias are fascinating plants belonging to the Asclepidaceae, or milkweed family, and are widely distributed in the tropical regions of the Old World. Between 160 and 200 species of Ceropegia have been described. Many of the species exhibit some level of succulence - usually in tuberous roots, but there are a number of species with succulent stems and semi-succulent leaves. The overwhelming majority of the Ceropegias produce very long vining stems which typically climb through the shrubby vegetation amongst which they grow. There is only one, or perhaps two species which can claim any degree of mainstream popularity: most of the other species which have managed to find their way into cultivation are grown by a small percentage of devoted growers, who grow these plants for their remarkable flowers, which are arguably amongst the most elaborate and unusual of the entire family.

   Ceropegias typically producing long tubular flowers with a bulbous base; the floral tube ends with 5 highly modified corolla lobes, whose tips may be fused together to produce an egg-beater, or birdcage-like structure. In some species, the corolla lobes are said to resemble parachutes, lanterns, and parasols. Linnaeus himself had one of the more curious associations, likening the appearance of the flowers to a fountain of wax: he derived the name "Ceropegia" from 'keros' meaning wax and 'pege' meaning fountain.

   As a rule, the flowers are not particularly colorful; in many species the flowers are greenish-white with purplish spots and streaks - but their unusual forms more than make up for their limited palettes. The flowers are actually traps which capture insects - sometimes imprisoning then for up to several days. But these flowers are not carnivorous, instead, this is a strategy to help insure that any insect which is lured into the flower will eventually transfer pollinia to the receptive stigma lobes. Like so many of the other succulent members of the greater milkweed family, the flowers of the Ceropegias are typically foul scented. The scents, flower colors, and "hairy" corollas of some species essentially mimic "road kill" to attract carrion flies to their flowers. These flies push their way past the corolla lobes, and work their way down the floral tube to the bulbous base of the flower, which contains the stigma lobes and anthers. The elaborate structures of the corolla lobes will only admit insects of a specific size, and will also help to prevent any premature escapes. The floral tube bears numerous downward pointing hairs which also prevents insects from climbing out of the flower. In trying to find an exit from the flower, the insect will inevitably encounter the stigma lobes, and will also blunder into the anthers, picking up one or more of the pollinia - waxy packets typically containing hundreds, if not thousands of pollen grains.

    In time, the downward pointing hairs in the floral tube will become more flaccid, and the petioles which once held the flower upright when the flowers first emerged, will tend to droop, leaving the flowers hanging upside down, giving any trapped insects an opportunity to escape. It is only when the escaped insects enter into a second flower (possibly becoming trapped a second time) that cross pollination can occur. As with most species of the milkweed family, the various species of Ceropegia tend to resist self-pollination, so that, more often than not, at least two genetically distinct individuals are needed for successful pollination - otherwise plants may be unlikely to set seed.

   In all of my years of growing succulents, I believe that I have only grown 4 species of Ceropegia, including C. ampliata, C. cimiciodora, C. woodii and this species. This is not because I don't appreciate the plants of this fascinating genus, or because they offer any particular challenges to cultivation: most of the species in cultivation are easy to grow, and many species will produce significant growth every year. The problem has been that the most unusual species tended to produce long, tangled vines which could grow many feet in length - and, left to their own devices, would insinuate themselves throughout my collection of plants. As much as I desired to grow some of these plants, I really could not properly accommodate their extensive vines. But a number of years ago, when I spied a few cuttings of this plant at the Greenhouse of Out of Africa (back in the days when this company was still located in Centerburg, Ohio), I could not resist it.

    This species originates from Madagascar, and belongs to a complex that includes a number of similar species and varieties with comparable, dimorphic stems. All of these plants produce a characteristic succulent stem in its vegetative stage; the stems at this stage are typically highly succulent, compact are comparatively short. but eventually, once the plant has sufficiently matured, it begins its reproductive stage, and at this time, it produces thin, long, cylindrical stems which typically climb to several yards, and produce numerous terminal flowers, with the curious vase shaped floral tubes, topped with a distinctive birdcage dome of petals with their tips united

   The succulent stems of this species are a truly bizarre form, looking like a complex hybrid of a zipper, grappling hook, and a boat anchor. Presumably, the strange shape of the stems enable this plant to find support in shrubby vegetation. Plants in cultivation will tend to produce more scrambling growth, seldom growing upright more than a few inches tall. Habitat photographs of related species show that the stems may grow vertically to perhaps 8 inches in height on their own, and taller with the support of other plants. The stems are cryptically colored with tans, pinks and dark greens, but the overall impression is that they have a greenish grey color that gives these stems an appearance of a dead stick. the odd "hooks" of the stem support very short lance-shaped leaves which are typically dropped within a few weeks or months - an adaptation to limit moisture loss during an extended dry season

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