| Stars and Blobs - Part 3
Family Asclepiadaceae, Tribe Stapelieae
The approximately dozen and a half species of Duvalia grow over a very wide area, with several occupying the Horn of Africa and east Africa , and most of the others found far to the south. The majority of South African species live in the eastern, summer rainfall, part of the country, with several found farther west in the Little Karoo and just a few reaching the winter rainfall regions of Namaqualand , the Richtersveld and southern Namibia . Most duvalias have a compact growth habit, their more-or-less angular stems so densely arrayed as to create a mat-like effect. The plants behave better in cultivation than many stapeliads, as they don't require ever larger containers and rarely rot suddenly for no discernable reason. Their flowers, generally not as striking as many of their relatives, typically consist of a five-lobed corona set into a circular disc bounded by an annulus, with five narrow outer corolla petals. Most of the modestly sized flowers lack brilliant colors or bizarre patterns, though a few species, such as the widespread Duvalia polita, do bear flowers with wide, colorful petals. In most cases though, with species such as Duvalia modesta or the western Duvalia pubescens (96.1224,Arid House) the flowers are more interesting than spectacular.
Also producing smallish flowers, the members of the small genus Piaranthus nonetheless have considerable horticultural value. The compact size of the plants, their relative ease of cultivation and the bright colors of their star-shaped blossoms all combine to make them one of the more satisfying stapeliad groups to grow. Though most species live in areas without summer rain, their range mainly lies south of truly arid regions; consequently they resist rot better than plants from harsher environments. Piaranthus punctatus (easy to grow despite its Namaqualand/Great Karoo home) has flowers that resemble little starfish with a bright yellow corona and petals buff-colored and heavily marked with striking red lateral stripes. Piaranthusatrosanguineus (formerly classified as Huerniopsis) has larger flowers--shaggy, velvety red and rather foul smelling. It and a second species of ex-Huerniopsis live well to the north of the others, in summer rainfall territory, but still manage to be more difficult to grow successfully than other Piaranthus.
The members of Echidnopsis, as originally constituted, had a strange, disjunct distribution, extending from Namaqualand all the way north and east to Somalia and Arabia , but with almost no representation in the huge middle of that range. In the mid-eighties the genus was divided in two. The northern plants were left as Echidnopsis and the few southern species are now called Notechidnopsis ("not" meaning southern, but also looking like just plain "not," a helpful reminder). The two genera resemble each other, with spineless stems divided in tesselations like a little corncob. The longish, narrow stems can either hug the ground or partly rise up. Their smallish, variably colored flowers remain close to the stem. The most widespread in cultivation, Echidnopsis cereiformis (from the Horn of Africa and Arabia ), grows easily, but the South African species (such as Notechidnopsis framesii) are considerably more difficult to grow and are uncommon in collections.
Many of the former species of Pectinaria (Arid House) have ended up either in the new genus Ophionella, or in a separate section of the older genus Stapeliopsis. In any case, these are small plants, mostly from western South Africa , with prostrate stems that sometimes burrow underground. Their distinctive flowers have petals that come together at their tips, looking like little orbs with slashed sides. In some very odd species of the group, the flowers are closed up so tightly as to resemble little apples. The flowers of Pectinaria articulatus, open at the truncated apex, look like a hollow five-lobed fruit cut in half; Stapeliopsis saxatilis has ovoid, reddish, almost tulip-shaped flowers, while the corolla tips of Ophionella arcuata gape open like a nestling bird with a five-lobed beak. None of the plants are particularly common or easy in cultivation; the couple of Namibian species moved into Stapeliopsis, with their flowers like open-ended urns, are quite difficult.
Crossing the ocean from Africa to the island of Madagascar brings us the genus Stapelianthus, with about half a dozen species. Stapelianthus flowers resemble huernias, usually open stars, often with bright colors and patterns. With stems covered by elongated, almost hair-like tubercles, Stapelianthus pilosus resembles Huerniapillansii. Stapelianthusmadagascariensis, its pale yellow flowers dotted with bright red dots, may be the most attractive species, and the most common in cultivation. Its mottled gray-pink stems have what I think of as the Madagascar colors, shared by a number of utterly unrelated Madasgascar plants and very few others anywhere. Stapelianthus are fairly rare plants, unable to withstand cold and susceptible to sudden rot if kept too wet in winter.
Perhaps the most spectacular stapeliad flowers, beautiful in an exotic way rather than just bizarre, belong to the genus Edithcolea. Native to Somalia , Kenya and northern Tanzania , both species of Edithcolea provide a challenge to anyone trying to grow them. The plants themselves differ from the others mentioned so far, with stiff, angular stems and fairly sharp little spikes at the tips of their tubercles. Edithcolea can form large clumps in the wild as they grow along the ground in hot, rocky, arid places. Their remarkable "Persian Rug" flowers are the reason for their persistent popularity in cultivation. These can stretch to six inches across, open stars with Gothic arch-shaped petals that terminate in graceful, pale yellow, lanceolate points. The rest of the flowers have an intricate network of purple and olive-green lines and are provided with fine hairs that give them an appearance of plush velvet. Unfortunately, simply keeping edithcoleas alive long enough to flower is quite difficult. The best results I've ever seen were achieved by growing them in a bed of little more than coarse sand with electric heating cables under the soil. Humidity, cold, excess water, will all prove quickly fatal to edithcoleas under less specialized conditions. Edithcolea grandis is best known; the smaller, drabber Edithcolea sordida (generally considered a subspecies of E. grandis) lives in Kenya and on the island of Socotra between Somalia and Yemen.
These numerous genera can frustrate someone just looking for a plant, yet specialist growers offer a wide selection of these stapeliads, and without some knowledge the result will be confusion. In terms of growing, the same general soil mix, fairly rich yet fast draining, will suit the easier plants of this group, while a much coarser mix with less organic material works better for the touchier species. Knowing the geographic origins of species and the rainfall patterns of those areas will make watering schedules more comprehensible, but remember that even winter growing species won't want water very often during stretches of daylong overcast and rain. Many of the winter growers can withstand considerable cold if they are dry and humidity remains low (a good trick to achieve), while plants from east Africa and Madagascar should never get too cold. We have a few of the plants in the Garden collection, although to be truly representative we could use a few more. A couple of the easier growing kinds may make it into sales from time to time.
Next month we'll finally make it to the true weirdos of this family! |
