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Aerangis thomsonii (Rolfe) Schltr., Beih. Bot. Centralbl. 36(2): 121 (1918).
Synonyms:
Angraecum thomsonii Rolfe in D.Oliver & auct. suc. (eds.), Fl. Trop. Afr. 7: 143 (1897).
Aerangis friesiorum Schltr., Notizbl. Bot. Gart. Berlin-Dahlem 9: 22 (1924).
Description:
Stem woody up to 10 mm diam., 10-100 cm long, usually upright, at least in the terminal leafy part, covered with old leaf bases in the lower part from which whitish roots up to 9 mm diam. arise. Leaves 8-20 alternate, distichous, 1-3 cm apart, ligulate, apex unequally lobed, the lobes rounded or obtuse, the longer 5-10 mm long, the shorter up to 5 mm long or absent, fleshy or leathery in texture, deep green, margins entire, 8-28 x 1-5-4-5 cm. Inflorescences borne at the nodes, arching racemes bearing 4-10 flowers; peduncle terete, up to 9 cm long, 6 mm diam., bearing 2 or 3 tubular sheaths; rhachis straight, green, to 20 cm long, with a short projection 2-3 mm long in the axil of each bract; bracts very broadly triangular-ovate, obtuse or apiculate, cucullate, 10-15 mm long. Flowers held erect in two rows, 1-5-3-5 cm apart, white, pedicel with ovary green, 3-6 cm long. Dorsal sepal erect, sometimes curving forward at the tip, lanceolate-elliptic, cuspidate, 22-30 x 7-9 mm; lateral sepals strongly reflexed, lanceolate elliptic, acuminate, winged on the back in the upper half, 25-32 x 5-6 mm. Petals reflexed, oblique, lanceolate-elliptic, acute, 20-25 x 6-8 mm. Lip reflexed, elliptic-lanceolate, acuminate, margins recurved below, inrolled above, 20-25 x 7-8 mm; spur pendulous, flexuous, cylindrical but widened and flattened in its terminal half, 10-15 cm long. Column erect, widened towards the apex, 6-8 mm long; anther cap conical, rounded; pollinia oblong; stipes very slender, 3 mm long; viscidium round.
Habitat:
The distribution of this orchid, which is the coolest growing Aerangis species, is restricted to the mountains of Kenya and northern Tanzania, and Uganda. It grows in deep shade as an epiphyte, often overhanging streams. Plants usually are found rather low on the trunks and branches of trees in upland forests at 5250-9850 ft. (1600-3000 m).
Notes:
Old plants of this species are easily distinguished from all others except Aerangis coriacea by their elongated, leafless stems. Aerangis coriacea, which occurs in some of the same forests as Aerangis thomsonii but usually at a lower altitude, also has a long woody stem in mature specimens, but the reticulate-venation of its leaves stands out from the upper surface in a much darker colour, whereas the leaves of Aerangis thomsonii are a concolorous green.
Cultivation:
Read more of cultivation of Aerangis thomsonii (Rolfe) Schltr.
Distribution:
SW. Ethiopia to E. Trop. Africa
References:
Hamilton, R. 1988. When does it flower? 2nd ed. Robert M. Hamilton, 9211 Beckwith Road, Richmond, B. C., Canada V6X 1V7. Kew Data Base. 2007. http.//apps.kew.org/wcsp/home.do la Croix, I. and E. la Croix. 1997. African orchids in the wild and in cultivation. Timber Press, Portland, OR. Stewart, J. and B. Campbell. 1996. Orchids of Kenya. Timber Press, Portland, OR. Stewart, J., J. Hermans, and B. Campbell. 2006, Angraecoid Orchids. Timber Press, Portland, OR; 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. 20.01-2017; http://apps.kew.org/wcsp/
Images:
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Photograph© Lourens Grobler. Image used with kind permission.	Photograph© Lourens Grobler. Image used with kind permission.	Photograph© Lourens Grobler. Image used with kind permission.	Photograph© Lourens Grobler. Image used with kind permission.	Photograph© Lourens Grobler. Image used with kind permission.	Photograph© Lourens Grobler. Image used with kind permission.