THE RHIPSALIDEAE: UNPOPULAR CACTI
translated from Russian by Irina Ten
The Rhipsalideae tribe belongs to a sub-family Cereoideae. Adapted to life in forest, members of the tribe usually grow as epiphytes on rocks and trees, in trees' crotches and hollows with the accumulated soil. The majority of species come from warm and damp areas of South and Central America. But there are some species that grow in the Old World (West and East Africa, Comoro Islands, Madagascar, Surinam, Ceylon). It is still unknown how the plants have got there.
The Rhipsalideae members are very diverse and decorative and they are particularly attractive in bloom when stems are covered with numerous, in some cases scented, flowers. Later, the shining beads of fruits appear.
Some species have large, unusually formed flowers. The Rhipsalideae members can bloom in fall, winter or early spring when other cacti hibernate. Some species bloom 2-3 times a year.
In collections these plants take the most shaded places and that means they don't "compete" with other plants that require bright light. The cultivation of the Rhipsalideae is quite simple. They grow fast, bloom readily and early, recover easily after a mechanical injury or disease (the affected branches can be just removed).
The most primitive genus Pfeiffera includes 4 species. They can be found in Bolivia and Northern Argentina in rather arid areas, on the ground not on the trees. The most common species in the collections is Pfeiffera ianthothele. Its soft ribbed pendent stems branch from the base and are densely covered with semi-transparent needle-like spines. White, funnelform flowers, up to 2 cm in diameter, appear in spring. The pinkish watery-transparent fruits are also covered with spines; the seeds are small, black and appear as a result of the self pollination.
For a long time taxonomists include only one species in genus Erythrorhipsalis - E. pilocarpa from Southern Brazil (Photo 1). This hardy, quite large plant has slender, firm, erect (later becoming pendant) stems with indistinct ribs and white short bristles cuddled to the stem. Lately a few species of the Rhipsalideae with short, slender and subtle stems were included in genus Erythrorhipsalis. Their bristles are diminished and sometimes absent. The most common species in collections is E. сеreuscula (Photo 2) but it will take some efforts to achieve vigorous growth and profuse blooming. Flowers of E. pilocarpa are pretty large, about 1.5-2.5 cm in diameter, cream with silky shine, fragrant. The base of stamens is pinkish. The plants bloom profusely 2-3 times a year (depending on cultivation conditions). Fruits appearing after cross-pollination are bright red and covered with bristles.
The habitat of the most numerous genus Rhipsalis matches the habitat of the whole tribe. Its members are very diverse. The species with slender stiff stems are best known among collectors. The most common species are Rh. baccifera, Rh. cassutha, not uncommon Rh. virgata and Rh. teres. The shoots are generally spineless and can be clearly divided into two groups: long (skeletal) and short, growing in whorls on the tops of elongated ones. Flowers are small, wide opened, and white; flowers of Rh. teres are bell-shaped, yellowish. Rh. capilliformis with many pendant very graceful, thin shoots is quite rare and often confused with other members of the group from which it can be distinguished by shoots growing from the top, not from the sides of segments.
Rh. mesembryanthemoides has very peculiar appearance: its skeletal segments branch near the top and otherwise short segments don't produce shoots and grow on all the surface of elongated ones arranged in spirals. All the short segments are of the same length and bear minute white needles. A plant resembles bushy branches of evergreens. A profuse and long lasting blossoming happens 2-3 times a year. Flowers are delicate, funnelform, and white. This is one of the most interesting and hardy species.
The plants with thick cylindrical shoots are very rare in genus Rhipsalis. They typically have ovary submerged into stem tissues. Dimorphism of shoots is less pronounced. Beautiful Rh. grandiflora has large, up to 2.5 cm in diameter, yellowish flowers, appearing occasionally in winter and early spring. Some taxonomists unreasonably place this group, as well as a species described below, into the genus Lepismium.
Areoles of Rh. paradoxa (Photo 3) are arranged in whorls by 3, with a well-pronounced rib under each one. The ribs in adjust segments are turned against each other and that adds beauty to its unordinary appearance. It grows fast but prone to deceases and not likely to bloom indoors.
The most beautiful among species with flat shoots is Rh. pachyptera. Its wide, thin, but stiff segments become reddish-violet under bright sun light. The large yellow flowers with the bunch of white stamens appear on the margins of segments.
Other two species with flat stems that grow well as house plants are Rh. crispata (Photo 4) и Rh. rhombea. The latter develops quickly into large specimens with long three-edged skeletal shoots. They bear numerous flat shorter segments. In bloom (often 2 times a year) the plant is densely covered with minute yellowish white flowers.
Some species usually belonging to genus Hatiora are sometimes included in genus Rhipsalis. The shoots of these cacti stay erect for a prolonged period of time and the plants resemble small trees with segmented woody stem and skeletal branches. The individual segments/shoots are short, club-shaped and branch only from the top. There occur funnelform, orange or yellow, waxy minute flowers. The most common species is H. salicornioides (Photo 5).
Genus Lepismium includes only one very variable species - L. cruciforme. Its long pendent flat, or three- to five-angled, shoots branch from the base of the cluster. The mature shoots produce new ones near the top. The ribs are deeply notched with areoles bearing small funnelform, red, pink or white flowers. In winter's lack of sunlight the plant can produce misshapen etiolated shoots. If removed they will not affect the blooming. The large red fruits of Lepismium are quite ornamental.
The remaining three genera of the Rhipsalideae are notable for ovary with more or less pronounced ribs. Acanthorhipsalis has flat lorate shoots with occasional cylindrical base resembling petiole. Flowers are medium-sized; the rarest species A. monacantha has orange flowers and A. houlletiana previously belonging to genus Rhipsalis has pale yellow, very neat bell-shaped droop flowers.
Rhipsalidopsis species can often be found in collections. Very attractive Rh. rosea has small, flat or ribbed segments with large pink, wide funnelform flowers. Noteworthy Rh. gaertneri (Photo 6) is sometimes mistakenly included by taxonomists into genus Epiphyllopsis. The flat segments of this species are large with prominent, long, reddish bristles on margins. The flowers are red, up to 8 cm in diameter, very neat, wide opening with long straight pistil surrounded by spiral stamens. The species is difficult in cultivation and is best grafted on Pereskia.
Lately the taxonomists include genera Zygocactus and Epiphyllanthus into genus Schlumbergera (Photo 7 & 8).
The most popular cactus in the tribe, Christmas Cactus is often mistakenly named Schlumbergera truncata. In fact Sch. truncata is quite rare and differs in its sharp-toothed segments, shorter flowers and ovary with less prominent ribs. The right name for Christmas Cactus is Schlumbergera bridgesii. It's most likely to be a hybrid and has many cultivar forms.