Species of the Month – November 2014
Dendrobium nanum (Hook.f.) Kuntze.
Synonyms: Callista nana (Hook.f.) Kuntze, Dendrobium mabelae Gammie
Etymology: The name Dendrobium is derived from Greek words “Dendron” meaning Tree and “Bios” meaning Life. It alludes to the epiphytic habitat. “nanum” is perhaps with reference to its small size.
Dendrobium nanum (Hook.f.) Kuntze. an epiphytic orchid not-so-commonly seen in many parts of Central and Southern Western Ghats in India. This species usually flowers in the months from September to November. Santapau and Kapadia (JBNHS vol 57) note that there 
are two distinct forms of the species.
Flowers are small usually found in erect inflorescence. Spur short and labellum greenish and lobes fringed. Pseudobulbs short and inflorescence is seen on the apexial nodes of the pseudobulb.
These are quite smallish plants, erect epiphytes and with old pseudobulbs devoid of any leaves. Membranous sheaths can be seen on the pseudobulbs. Every season fresh pseudobulbs emerge and with it new inflorescence. These are usually found at the elevation of 1000m in the sub-montane zone.
Unlike other bigger flowered Dendobiums, these are not very popular in culture. It could be due the specific climatic requirements like temperature, humidity etc of the plant. 
These requirements make it difficult to achieve in greenhouse/garden environment.
Threats: Several threats posed for these species (for a lot of other species as well) in the wild, including road widening and logging in the Western Ghats region. Due to the inconspicuous nature of the species it makes it difficult to take notice for a untrained eye. There are also cases of people collecting the plants for their beautiful flowers, but without proper knowledge of culture requirements they perish soon after.
References:
1. Critical notes on the Orchidaceae of Bombay State – Santapau and Kapadia
Article by: Ravee Bhat