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Orbea namaquensis (N.E.Br.) L.C.Leach

Family: ASCLEPIADACEAE

Publication: Kirkia 10: 290 1975

Description

Orbea namaquensis, firstly described as Stapelia namaquensis by N. E. Brown in 1882, is a leafless perennial forming small clumps or mats. The stems are very similar to those of Orbea ciliata with stout conic teeth loosely arranged in 4 rows, but the flowers are different. 1-4 flower up to 10 cm in diameter are produced in succession on lower stem, inside they are irregularly transversely ridged, pale greenish yellow, irregularly marked with dark purple-brown. The annulus almost as wide as limb, is finely tuberculate, with margin completely recurved. This species appear to be very variable in colour, ciliation and outer corona-lobes as the related Orbea variegata, from which it mainly differs in the internal flower structures and the annulus.

Stems: Short, stout, sometimes almost cylindrical, 4-8 cm long, 15-18 mm thick, excluding the teeth, squat, shortly prostrate and then decumbent, distinctly 4-angled. Tubercles (teeth) stout, 3-10 mm long, spreading,conical, acute, glabrous, green, prettily marked with irregular purple stripes where exposed to the sun.

Leaves: Rudiments hardened.

Inflorescences: 1- to 4-flowered, near the base or middle of the young stems. Flowers successively developed.

Flowers: Pedicels, glabrous, striped with darker purple-red, 2 mm long, 0.5 mm in diameter. Sepals 4-6 mm long, 2.5 mm, ovate, acuminate, glabrous. Corolla in bud depressed-pentagonal with a very acuminate point, when expanded 7.5 - 10 cm across, basin-shaped, tube embracing the corona, shortly hairy at the base, pale greenish-yellow, vertically broadly streaked with dark red-brown, partly marked with confluent spots or reticulate. Annulus large, almost as wide as limb, very prominent solid-looking, fleshy, margin extremely recurved or revolute so as to be nearly circular in transverse section, and the bottom of its cup densely covered with short erect stiff purple-brown hairs and minutely tuberculate-rugose. Back smooth and glabrous. Corolla-lobes 3 x 2.5 cm, divaricate, revolute, not ciliate or sometimes finely ciliate, inner surface plicate-rugose or papillose, papillae, pale greenish-yellow, everywhere covered with dark purple-brown thick transverse lines or rounded or transverse or confluent spots or labyrinthine markings.

Corona yellow with red-brown spots. Outer corona-lobes elongate-rectangular, 6-8 mm long, 1.5 mm wide, ribbon-like, spreading then ascending, attenuate entire to trifid , acute, yellow, dotted with purple-brown. Inner corona-lobes 3.5-5 x 1 mm, narrowly ovate, erect, apical appendage filiform, clavate, overtopping the style head, sometimes tips revolute, partly with a dorsal hump, but without an outer horn. Nectar slit drop-shaped. Pollinia 0.8 x 0.5 min, bean-shaped.

Blooming season: Summer-autumn and the flowers remain expanded for 3–4 days.

Fruits (follicles): to 15 cm, 1,8 cm thick, subparallel, fusiform, acuminate, glabrous.

Chromosome number: 2n = 22

Origin and Habitat

Orbea namaquensis is restricted to Namaqualand (Northern Cape) in the northwestern corner of South Africa where it can become locally quite common.

Habitat and ecology: It growos together with a rich succulent flora comprising Stapelia pulvinata, Stapelia barklyi, Bulbine praemorsa, Tylecodon wallichii, Tylecodon racemosus, Tylecodon reticulatus, Lampranthus hoerleianus, Antimima radicans, and Ottosonderia monticola.

Cultivation and Propagation

Orbea namaquensis is one of the easiest stapeliads to grow. It like a half-sun or shaded position (never grow in too harsh sun), very resistant to heat will also tolerate quite cold temperatures but avoid frost, best in a ventilated environment. It is quite resistant to the “Balck spot” disease of Asclepiads, Water regularly during the growing season, keep dry in winter. Use a gritty, well-drained soil.

Propagation: It is easily propagated by removing a cutting, sometimes with roots attached, in spring and summer, but seeds germinate readily if they are sown when fresh.

Bibliography

Major references and further lectures

  1. Focke Albers, Ulrich Meve “Illustrated Handbook of Succulent Plants: Asclepiadaceae: Asclepiadaceae”Volume 4 Springer, 2002

  2. N. E. Brown “Flora Capensis” Vol 4, 1909

  3. “Hooker’s Scones Plantarum” 1908 (1890)

  4. Lückhoff “The Stapelieae of southern Africa” 153 (1952)

  5. Lamb & Lamb, “Illustrated reference on cacti and other succulents” 3: 881 (1963)

  6. Court, “Succulent flora of southern Africa” 141 (1981)

  7. James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11 August 2011

  8. Ernst Van Jaarsveld, Ben-Erik Van Wyk, Gideon Smith “Succulents of South Africa: A Guide to the Regional Diversity”Tafelberg, 2000

  9. John Manning “Field Guide to Wild Flowers of South Africa, Lesotho and Swaziland” Struik Nature, 2009

  10. Matlamela, P.F. & Kamundi, D.A. 2006. Orbea namaquensis (N.E.Br.) L.C.Leach. National Assessment: Red List of South African Plants version 2015.1. Accessed on 2016/05/20

  11. F. Albers and U. Meve “Mixoplidy and cytotyped: a study of possible vegetative species differentiation in stapeliads (Asclepiadaceae)” Bothalia 21(1): 67-72 (1991)