Dendrobium section Grastidium (Blume) J.J.Sm.,
Orchid. Java (1905) 348.
Rhizome usually short. Stems elongated and slender, not fleshy, many-leaved, usually unbranched, sometimes strongly bilaterally flattened. Leaves sheathing at the base, long-lived, glabrous, very rarely the sheaths hairy (Dendrobium setosum). Inflorescences lateral from the stem, very short, 2-flowered, the peduncle enveloped by a pair of conduplicate, imbricating scale-leaves. Flowers small to rather large, resupinate or not, usually ephemeral, those of a pair often facing each other, opening synchronously. Mentum (rather) short and broad. Lip not or somewhat mobile.
Sri Lanka, continental tropical Asia, Taiwan, Malaysia, Brunei, the Philippines, Indonesia, Papua New Guinea, Solomon Islands, Vanuatu, New Caledonia, Fiji, Samoa, Tahiti. About 180 species; in New Guinea c. 125 species.
Epiphytes in lowland and montane forest.
Grastidium is an extremely diverse and species-rich section, which is urgently in need of revision. As a rule it can be recognised by the short, 2-flowered inflorescences that arise laterally from the stems from between a pair of flattened, short-lived but peristent, overlapping scale-leaves. The stems, though sometimes quite stout, are never fleshy, but of uniform thickness and leafy throughout. These meagre facts are about all that the numerous species have in common. It is probably true to say that the flowers of Grastidium show more variation than all other dendrobiums combined. While many are more interesting than beautiful, quite a few are highly attractive. It is a great pity, therefore, that the flowers in almost all species last only a single day, and not even a whole day. On the other hand, they usually flower four or five times a year, or even more frequently, and then all flowers on a plant and on all plants in the area, open synchronously.