Crassula sericea var. sericea
Introduction
Crassula sericea var. sericea is a common cliff-dwelling succulent shrublet in southern Namibia and in the lower Gariep (Orange River) region in the Northern Cape.
Description
Description
A much branched succulent shrublet up to 200 mm high forming rounded spreading clusters up to 200 mm in diameter. The leaves are very fragile, variable in shape and size, mainly inversely egg-shaped to almost orbicular, 10-25 ×10-25 mm, very swollen after rain, becoming somewhat flattened (dorsiventrally compressed) during drought; the upper surface is flat to rounded (convex) and the lower surface rounded. The leaf margins are reddish in the upper part and the surface grey-green with spreading, to recurved hairs. The leaf base is wedge-shaped and the apex is blunt (obtuse).
The flowers are small and arranged in an elongated inflorescence 40-100 mm long bearing few to many flower clusters (dichasia). The inflorescence stalk is hairy and purplish at the base. The floral calyx has triangular to spear-shaped (lanceolate) lobes 1 mm long. The flowers are small, without a flower stalk, about 4×2 mm, the petals 3×1.3 mm, white and spreading. Its stamens have brownish anthers (pollen bearing part). Crassula sericea var. sericea flowers mainly during Winter (May-August).
Distribution and habitat
Distribution description
Crassula sericea var. sericea is found in the lower Gariep (Orange River) Valley from Kakamas in the east to the Richtersveld (Northern Cape, South Africa) in the west and in the Hunsberg, Karasberg and Witputz regions of Namibia. The plants are confined to sheer cliff faces, up to about 800 m in altitude, where they grow in crevices with shallow soil, mainly on quartzitic sandstone rock formations. Temperatures in the region are high during summer and mild in winter. Rainfall in the western Richtersveld region occurs mainly during winter (cyclonic winter rain) and in the eastern part (Bushmanland) mainly during summer. It ranges between 75-250 mm per annum. Plants grow on shady rocky ledges in shallow soil. The associated vegetation consists of Succulent Karoo and Desert biomes. The Richtersveld and the adjacent territory is a centre of endemism for the family Crassulaceae to which the species belongs (many species are confined to this region). In the upper reaches of the Gannakouriep River (Ai-Ais Richtersveld Transfrontier National Park) Crassula sericea var. sericea was found growing with other cliff-dwelling succulent plants such as Tylecodon ellaphieae, Aloe meyeri, Bulbine pendens and Ornithogalum suaveolens.
Derivation of name and historical aspects
History
Crassula sericea var. sericea was named by Selmar Schönland in 1910 from plants collected by the German plant explorer, Rudolph Schlechter. The specific epithet sericea, is Latin and means 'silky' and pertains to the dense silky hairs on the leaves of this species.
Crassula sericea var. sericea is one of about 170 Crassula species occurring in South Africa and Namibia, and belongs to the Stonecrop family (Crassulaceae). It is closely related to C. sericea var. velutina and C. sericea var. hottentotta. Crassula sericea var. velutina has larger flattened leaves with velvety hairs and flowers from September to November (Spring flowering). Crassula sericea var. hottentotta has rounded leaves similar to those of var. sericea but not brittle and it can also be distinguished by its leaf surface which bears coarse rounded papillae, and is thus not hairy as in the other varieties. The plants also flower during winter (June-August).
Ecology
Ecology
Plants have a clustered and compact growth against the cliff (cliff hugger) and are well adapted to the sheer habitat. They are winter growers, the leaves are brittle and when becoming dislodged, will root in crevices establishing new clones. The grey-green very succulent leaves covered with short spreading hairs are an adaptation to the dry habitat. The small white flowers are pollinated by insects.
Uses
Use
No uses have been recorded.
Growing Crassula sericea var. sericea
Grow
Propagation: Best grown from leaf cuttings during autumn. They can be planted in sand and kept moist, in a sunny or partially shaded region. Rooting is rapid and leaves will proliferate from their base. They can be planted out directly to the chosen container.
Cultivation: Best suited for summer-dry succulent karroo gardens on shady rockeries. Outside of its habitat it should preferably be grown as a pot plant in a greenhouse under controlled conditions. The plants tend to get fungal rust infection in coastal parts (Cape Town coast).
References
- Toelken, H.R. 1977. A revision of the genus Crassula in southern Africa. Contributions of the Bolus Herbarium no. 8, part 2. Bolus Herbarium, University of Cape Town, Republic of South Africa.
- Toelken, H.R. 1985. Crassulaceae: Flora of Southern Africa vol. 14. (Ed. O. A. Leistner). Botanical Research Institute.
- Rowley, G.D. 2003. Crassula. Cactus & Co. Libri.
Credits
Ernst van Jaarsveld
Kirstenbosch National Botanical Garden
August 2009
Plant Attributes:
Plant Type: Perennial, Succulent
SA Distribution: Northern Cape
Soil type: Sandy
Flowering season: Winter
PH: Acid
Flower colour: White
Aspect: Full Sun
Gardening skill: Challenging
Special Features:
Drought resistant
Good potplant
Horticultural zones
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