Rossioglossum williamsianum [Rchb.f] Garay & Kennedy 1976 Photo courtesy of © Lourens Grobler

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Common Name William's Rossioglossum [Englsih Orchid Nurseryman 1800's]

Flower Size to 6" [to 15 cm]

A medium to large sized, warm to cold growing epiphyte found on trees in dense forests at elevations up to 1000 meters with oblong-ellipsoid, laterally compressed, ancipitous pseudobulbs enveloped basally by 2 or more, large sheaths and carrying 1 to 2 apical, arching, elliptic, coriaceous, subacute or obtuse, shortly grooved petiolate leaves that blooms on an axillary, erect, to 12" [30 cm] long, several [to 8] flowered inflorescence arising on a recently matured pseudobulb along the axil of a basal sheath with spathaceous, subacuminate bracts occuring in the spring and summer and is a rare find in Mexico, Guatemala and Honduras?.

The easiest way to identify this species when the lip can be viewed well is the thin, elongate, recurved, reddish column wings instead of the yellow, flabellate, pubescent, suborbicular column wings of the more common R grande. Of course there are many other differences including a longer inflorescence with more flowers but the column wings are diagnostic

Synonyms Odontoglossum grande var. williamsianum Rchb.f 1886; *Odontoglossum williamsianum Rchb. f. 1881;

References W3 Tropicos, Kew Monocot list , AOS Bulletin Vol 33 No 11 1964 as Odontoglossum williamsonianum; Las Orquedias de El Salvador Vol 3 Hamer 1981; Fieldiana Biology, Flora Costa Ricensis Family # 39 Orchidaceae, subtribes Maxillariinae and Oncidiinae Atwood & Mora 1997; The Pictoral Encyclopedia of Oncidium Zelenko 2002; AOS Bulletin Vol 73 No 6 2004 photo; Orchid Species Culture: Oncidium, Bakers 2006; Icones Orchidacearum 5 - 6 Orchids of Mexico Part 2 - 3 Plate 663 Hagsater & Soto 2002; Orchid Digest Vol 71 No 1 2007 photo; AOS Bulletin Vol 78 No 5 2009 photo

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