Brachystelma modestum R.A.Dyer
Common names: none known
The name modestum appears well deserved by this diminutive species of Brachystelma since the flowers are so astonishingly attractive, while the plant itself is hidden in grassveld in shallow soil among rocks.
Brachystelma modestum is a perennial, dwarf herb with a tuberous rootstock. The tuber is 20-30 mm in diameter, fairly rounded on the underside. Stems are simple or branched near the base, slender, 1-2 produced annually, 20-30 mm high. Leaves are 10-30 x 5-10 mm, in 3-5 pairs with a short leaf stalk, venation is prominent on the lower surface and impressed on the upper surface. Flowers are small, cup- or bell-shaped, 1 or 2 together, developed one after another; in bud they are greenish and red-spotted, about 5 x 10 mm; in flower they are parchment-coloured within the tube with transverse dark stripes; lobes are velvety-maroon or chocolate-purple. The plants have a long flowering season in habitat, lasting from October to late March with a peak from November to the beginning of February.
Brachystelma modestum is listed as Near Threatened (NT) on the Threatened Species Programme's Red Data List and is currently not conserved in any formally protected area. This species is restricted to drier sandstone grasslands in areas that are mostly unsuitable for the growing of crops. These areas have traditionally been utilized as communal rangelands. However, with increasingly dense rural populations in KwaZulu-Natal, the pressures on these grasslands have increased with the growing numbers of livestock grazing the land.
The shallow soils on which this species grows are particularly sensitive to trampling by cattle. This is likely to cause an ongoing decline in the number of mature individuals with increasing numbers of livestock grazing the sandstone grasslands. In the Umzinto District, much of the sandstone grasslands have been converted to pine plantations and sugarcane.
Distribution and habitat
This species occurs in rocky areas covered with short grassveld, the plants frequent soil pockets between the rocks. Brachystelma modestum owes its survival in this habitat to its small, perennial, tuberous rootstock which escapes damage during grass fires. It appears to be rare and restricted in its distribution.
Although confined to the Natal Group sandstone region of central-south KwaZulu-Natal, historical records include Nkandla, Kranskop, the Noodsberg and Umzinto, and recent surveys report Inanda, Eston and south of Durban as additional localities (David Styles pers. comm.).
Derivation of name and historical aspects
The exact numbers of species within the genus Brachystelma is not known but may be up to 100. Brachystelma occurs from Africa to India and Burma, but predominantly in southern Africa where nearly 70 species are found; most species are widespread but rarely common except sometimes locally.
B. modestum in its typical, minute, upright form is readily distinguished from its near allies, but records show that it does vary in habit over its range of distribution. Under cultivation the deviation from normal is even greater.
Pollinator is not known, it is possibly pollinated by flies.
The tubers of practically all species of Brachystelma are edible and sought after by man and certain animals. This has almost certainly played a part in bringing about the present distribution of species and the low density of plants. Brachystelma species, as with certain other genera in the family Apocynaceae are sought after by private collectors.
Growing Brachystelma modestum
Although Brachystelma modestum occurs in a high-rainfall region, where rain may fall regularly in the summer months, the thin sandy substrate upon rock in which it grows does not hold moisture and dries out rapidly. Tubers remain damp for only brief periods. It is difficult to replicate this environment in cultivation. For this reason, and like certain other Brachystelma species with tubers, they require high maintenance and are prone to attacks by fungi and mealy bug.
Brachystelma modestum is best grown in shallow terracotta pots or asbestos trays in morning-only sunlight or light shade with the tuber partly exposed. The best germination medium is a fairly heavy soil since this retains some moisture for longer periods than sandy soil, in the shallow containers. Pots should be watered occasionally in winter months to prevent the tubers from shriveling. Seeds generally germinate within two weeks after sowing and watering, but this process is variable and can take up to almost five weeks. Plants should not be over-watered.
- Craib, C. 1993. Field studies and cultivation of some Brachystelma species in the Eastern Cape, Natal, the eastern Free State (including Qua Qua) and the Transvaal. Excelsia 16: 11-23.
- Dyer, R.A. 1954. Brachystelma modestum. The Flowering Plants of Africa 30: t. 1165a.
- Dyer, R.A. 1980. Asclepiadaceae ( Brachystelma, Ceropegia, Riocreuxia ). Flora of southern Africa 27, part 4.
- Dyer, R.A. 1983. Ceropegia, Brachystelma and Riocruexia in southern Africa. Balkema, Rotterdam.
- Scott-Shaw, R. 1999. Rare and threatened plants of KwaZulu-Natal and neighbouring regions. KwaZulu-Natal Nature Conservation Service, Pietermaritzburg.
- Threatened Species Programme Red List database, SANBI. www.sanbi.org
Threatened Species Programme
Plant Type: Bulb, Perennial
SA Distribution: KwaZulu-Natal
Soil type: Sandy, Loam
Flowering season: Early Summer, Late Summer
Flower colour: Purple, Red
Aspect: Morning Sun (Semi Shade)
Gardening skill: Challenging