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Plant Highlight: Stapelia hirsuta
by Brian Kemble
About the genus and area of occurrence
The term stapeliads is used to refer to a large group of plants in the family Apocynaceae, typically with clusters of ascending leafless succulent stems and remarkable 5-pointed flowers. While formerly placed in the Asclepiadaceae, or Milkweed Family, they are now included within a broadened concept of the Apocynaceae. The name is taken from the genus Stapelia, though it includes a host of species in many different genera. While it is not always easy to distinguish between the various genera, in general the species in Stapelia differ from other stapeliads in having velvety stems. While various classifiers have differed greatly in the number of species recognized in the genus Stapelia, the authoritative work Stapeliads of Southern Africa and Madagascar, published in 2005, lists 28 species as well as quite a few varieties. These are found over a large area in southern Africa. Some of the species have exceptionally large flowers; an example is Stapelia hirsuta, native to the winter-rainfall region in western South Africa and eastward into the Little Karoo and Eastern Cape Province.
About the plant
Stapelia hirsuta is clump-forming, with erect (or nearly erect) velvety four-sided stems, these being 2 to 12 inches (5 to 30 cm) long. Some populations have longer stems than others overall, but it is also true that plants in shadier positions tend to have longer stems than those in the sun. Along each of the angles (the corners between the faces of the stem) there are conical or bluntly four-sided tubercles at regular intervals. Each tubercle is initially surmounted by a tiny fleshy projection which is actually a rudimentary leaf, but this eventually withers and leaves a small gray scar in its place. The stem diameter is .4 to .8 inch (1 to 2 cm), and its texture varies from very minutely fuzzy (or even smooth) to conspicuously velvety, with smoother-stemmed plants predominating where plants are found on sandstone, while velvety-stemmed plants predominate on shale. The stem color is green or grayish green, sometimes tinged or mottled with red, especially on plants in more exposed positions. Older specimens can have many stems and reach a diameter of 1 foot (30 cm) or even more.
About the flowers
This species flowers in the latter part of summer and into the autumn months. A short fuzzy inflorescence (less than .2 inch long, or 5 mm) emerges at the base of a stem, bearing one to three flowers. Each flower has a pedicel (the stalk of the individual flower) that extends out from the plant and curves up at its tip, so that the flower is facing upward. The pedicel varies in length from .8 inch to 2.75 inches (20 to 70 mm), or occasionally even more than this. At the bud stage, each developing flower looks like one of the onion domes seen atop a Russian Orthodox church, with 5 facets. At maturity, it splits open along the seams to yield a 5-pointed star, with the five spreading lobes joined into a cup at the center. This large outer part of the flower is the corolla, and within the central cup is the much smaller corona, containing the reproductive parts. The corona rises mushroom-like from the base of the cup, with its central pistil, 5 stamens, and attendant lobes all fused into an elaborate structure called a gynostegium. The flower (as is the case with many species among the stapeliads) has a powerful foul smell to attract the flies that pollinate it. The flower diameter in Stapelia hirsuta is quite variable, ranging from 2 to 5½ inches (5 to 14 cm). The face of the flower is roughened by many small transverse ridges, with the roughness usually decreasing toward the tips and also toward the center. The flower color is purple-red to dark maroon, often with narrow bands of light yellow on the rough part, while the tips are typically uniformly dark. On some plants there is a yellowing at the center, surrounding the darker purplish-red of the corona. The flowers are usually hairy, but there is much variation in this feature as well. In some populations, the center of the flower has a dense mass of long purplish-red hairs, with the corona emerging from among them. In other populations, the hairs are mostly at the margins of the flower, and sometimes they are absent altogether. The width of the corolla lobes also varies, with the lobe margins sometimes curling under so that the lobes are narrowed.
An anomalous six-pointed flower.
About the fruits
If pollinated, a flower develops a pair of tapered-cylindrical follicles with purple markings; these are typically about 6 to 8 inches long (15 to 20 cm). They have a seam running lengthwise that eventually splits open when the seeds are mature. The flattened papery seeds have a tuft of fine hairs that allow them to be dispersed by the wind.
Plants in cultivation
Stapelia hirsuta is not a difficult plant to grow if provided with a fast-draining soil mix and kept from extended below-freezing temperatures in winter. It likes plenty of sun (to keep it compact and bring out the red or purple tinges in its stems), and it does well either in a pot or in the ground where winters are not too cold. Because the seeds are wind-dispersed, they can come up spontaneously some distance away from the plant that produced them.
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A flower with fewer hairs and narrower corolla lobes than usual.
