Aerangis luteoalba (Kraenzl.) Schltr., Beih. Bot. Centralbl. 36(2): 118 (1918).
Synonyms:
Angraecum luteoalbum Kraenzl. in H.G.A.Engler (ed.), Pflanzenw. Ost-Afrikas, C: 158 (1895).
Rhaphidorhynchus luteoalbus (Kraenzl.) Finet, Bull. Soc. Bot. France 54(9): 35 (1907).
Description:
Stem 1-3 cm long, often pendent with numerous thin flexuous roots which are relatively long for the size of the plant. Leaves 2-8, laying in one plane, linear-ligulate or linear-lanceolate, sometimes falcate, unequally bilobed at the apex, the lobes rounded, the shorter lobe sometimes suppressed, fleshy and brittle in the rainy season becoming leathery in the dry season, up to 15 cm long, 6-15 mm wide. Inflorescences arising from the stem below the leaves, arching or pendent racemes bearing few to 25 flowers in the upper half or two thirds, up to 35 cm long; peduncle slender, terete, bearing 2-3 sheaths; rhachis similar, slightly zigzag; bracts spreading or slightly reflexed, ovate, acute, 3-4 mm long. Flowers arranged in two rows all in the same plane, 7-20 mm apart; perianth parts all spreading, white, cream, greenish, or yellowish white; the column similar in colour, or bright red; pedicel with ovary slender, 1-2 cm long. Sepals oblanceolate, acute, 10-15 x 3-7 mm. Petals obovate or broadly oblanceolate, equaling or a little longer than the sepals, 5-10 mm wide. Lip obovate or rhomboid, widest above the middle, acute, 15-20 mm x 7-15 mm; spur slender, incurved, slightly thickened in the apical half, 2.3-4 cm long. Column short and thick, 2-3 mm long; androcilnium slightly sloping with frilly margins; rostellum projecting straight downwards; pollinia ovoid; stipes considerably widened in the upper half; viscidium oval or round. Capsule 2-2-5 cm long.
Habitat:
The species grows across equatorial Africa from Cameroons and the Congo Republic in the west through the central and western forests of Uganda to Somalia, Ethiopia and Kenya in the east. In Kenya, the plants are usually found at 3000-5000 ft. (910-1520 m) on the southern and southeastern slopes of Mt. Kenya and on the southern slopes of Mt. Elgon. Aerangis rhodosticta grows in warm, moist conditions, almost always in forests along rivers. Plants normally grow in areas well protected from drought, often near waterfalls. They usually grow on twigs and branches of shrubs, but are occasionally found on tree trunks.
Notes:
Kraenzlin mentioned the similarity of this species to Angraecum citratum Thouars (now transferred to Aerangis) of Madagascar. The small plants with long inflorescences, bearing flowers in two distinct rows but all in one plane, have some superficial resemblances but are easily distinguished. Aerangis citrata has much broader leaves and bears many more rather smaller flowers than Aerangis citrata luteo-alba. In the latter the sepals are all the same size and in the same plane whereas in Aerangis citrata citrata the dorsal sepal is much smaller than the others and leans forward parallel to the column. The lip of Aerangis luteo-alba has an acute apex and that of A. citrata is retuse.
Cultivation:
Read more of Cultivation of Aerangis luteoalba (Kraenzl.) Schltr.
Distribution:
WC. & E. Trop. Africa to Ethiopia
References:
Beaton, C. 1985. Indoor light culture for Aerangis rhodosticta. American Orchid Society Bulletin, 54(8):963. Bechtel, H., P. Cribb, and E. Launert. 1980. Manual of cultivated orchid species. MIT Press, Cambridge, Mass. Cavestro, W. 1980. Aerangis rhodosticta (Krzl) Schltr. - An African pygmy. American Orchid Society Bulletin, 49(5):509. Hawkes, A. D. (1965) 1987. Encyclopaedia of cultivated orchids. Faber and Faber, London. Hillerman, F. 1986. Growing Aerangis Orchids. American Orchid Society Bulletin, 55(8):803. Hillerman, F. E., and A. W. Holst. 1986. An introduction to the cultivated Angraecoid orchids of Madagascar. Timber Press, Portland, Ore. Northen, R. T. 1980. Miniature orchids. Van Nostrand Reinhold, New York. Piers, F. 1968. Orchids of East Africa-Nairobi, Kenya. Verlag von J. Cramer, 3301 Lehre. Stewart, J. 1984. Growing Angraecoid orchids - Part 1 - Introduction. American Orchid Society Bulletin, 53(7):731: A Revision of the African Species of Aerangis (Orchidaceae) Kew Bulletin, Vol. 34, No. 2 (1979), pp. 239-319;WCSP (2017). 'World Checklist of Selected Plant Families. 19.01-2017; http://apps.kew.org/wcsp/
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