Sobennikoffia robusta (Schltr.) Schltr., Repert. Spec. Nov. Regni Veg. Beih. 33: 362 (1925).
Oeonia robusta Schltr., Ann. Inst. Bot.-Géol. Colon. Marseille, III, 1: 184 (1913).
Angraecum robustum (Schltr.) Schltr., Beih. Bot. Centralbl. 33(2): 427 (1915).
A robust epiphyte or lithophyte that grows to more than 16 in. (40 cm) tall. Numerous roots that are very long, white with green tips, often aerial, and 0.2 in. (0.4-0.6 cm) in diameter are produced. Pseudobulb/stem: Old plants may have stems that do not commonly branch and are 10-16 in. (25-40 cm) long by 0.4-0.6 in. (1.0-1.5 cm) in diameter. The lower portion of the stem is covered with brown leaf sheaths. Leaves: 10-15 in. (25-38 cm) long by 1.0-1.4 in. (2.5-3.5 cm) wide. Numerous very leathery, strap-shaped leaves with unevenly and bluntly bilobed tips are carried on the stem. The leaves, which are not glossy, are colored a medium green, have wavy margins, are fairly strongly ribbed, and are slightly to moderately keeled on the back. Inflorescence: Up to 20 in. (50 cm) long, with an upright, rigid peduncle that is clad with several sheaths and is about 0.1 in. (0.3 cm) in diameter. Flowers are carried in a loose cluster, each with a floral bract that is oval, bluntly pointed, and much longer than the up to 1.2 in. (3 cm) long pedicel. Flowers: 12-17 per inflorescence. The flowers, which are white but turn yellowish with age, are about 2.4 in. (6 cm) across and 2 in. (5 cm) tall and have sepals and petals that are recurved, especially at their tips. Sepals are lanceolate-elliptical with sharply pointed tips. The dorsal sepals is up to 1.4 in. (3.5 cm) long by 0.6 in. (1.4 cm) wide near the base. The curved, sickle-shaped lateral sepals are up to 1.6 in. (4 cm) long by 0.4 in. (1.1 cm) wide. The broadly sickle-shaped petals s are sharply pointed, more or less horizontally spreading, have sharply pointed tips, and measure up to 1.4 in. (3.5 cm) long by 0.5 in. (1.3 cm) wide near the base. The 3-lobed lip is concave but does not embrace the column. It is up to 1.8 in. (4.5 cm) long by 1 in. (2.5 cm) wide. The center lobe is 0.6 in. (1.5 cm) long, while the two outer lobes are about 0.4 in. (1 cm) long. The rear portion of the lip forms a wide spur which turns upward and is about 1.8-2.0 in. (4.5-5.0 cm) long. The spur is about 0.3 in. (0.8 cm) broad at the entrance but tapers rather sharply to about 0.08 in. (0.2 cm) wide within a distance of about 0.6 in. (1.5 cm) of the entrance. The column is tall with rather square earlike appendages.
This orchid is found in the western portion on the island where it has been found near Mahajanga at 4900-6550 ft. (1500-2000 m). It grows on or at the foot of trees and shrubs in woody areas with sandy soil in a region where there is a significant dry season. Plants usually are epiphytic or lithophytic, but they may occasionally be found growing as terrestrials.
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While not a small plant, Sobennikoffia robusta is certainly no giant Angraecum eburneum type, and is comparable to medium-sized cattleyas. This little known species deserves a place in every good collection. It blooms in late May and early June, and its well-arranged flowers form spectacular sprays, with 2 or 3 inflorescences per plant. The sepals and petals of the showy flowers are gracefully recurved. The flowers are white with a slight greenish tint on the back sides as well as on the midrib of each segment. The spur is quite greenish, as is the throat of the flower. As they age, the flowers turn a rich apricot color, which may be maintained for several weeks. This color also appears when the flower is pollinated. These green “cool white” flowers, which last at least one month, are immediate eye catchers, and prove to be conversation pieces at any showing. Add to this picture a subdued spicy scent in the evening hours, and you have a sure award-winner. Long blooming and frequent blooming orchid species.
De la Bathie, H., and H. Humbert. [1939, 1941] 1981. Flora of Madagascar 1-2. The Government of Madagascar and the National Museum of Natural History, Paris. Translated and published in 1 vol., Steven D. Beckman, 621 Palm Ave., Lodi, CA, U.S.A. 95240. Du Puy, D., P. Cribb, J. Bosser, and J. and C. Hermans. 1999. The Orchids of Madagascar. The Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AB, England. Hamilton, R. 1988. When does it flower? 2nd ed. Robert M. Hamilton, 9211 Beckwith Road, Richmond, B. C., Canada V6X 1V7. Hillerman, F. and A. Holst. 1986. An introduction to the cultivated Angraecoid orchids of Madagascar. Timber Press, Portland, Ore. 'World Checklist of Selected Plant Families. 15.03.2017; http://apps.kew.org/wcsp/
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