The following article was written for the Orchid Species Bulletin published by the Orchid Species Society, which is based in Brisbane, Queensland in September 2009.
Bear in mind that any cultivation notes refer to the sub-tropical conditions of Southern Queensland, Australia.
Dendrobium heterocarpum Wall.
ex Lindl. was collected by Nathaniel
Wallich in
Den. heterocarpum has spindle-shaped or subcylindrical erect or pendulous pseudobulbs that are 40-50 (-150) cm long and about 1 cm in diameter. The pseudobulbs are many-noded and are amber-yellow when older. Many deciduous oblong-lanceolate to tongue-shaped leaves are borne along the pseudobulbs in two ranks. The leaves are 7-11 (-18) cm long and 1.5-2.5 cm broad. Short inflorescences are borne from nodes along the apical half of the leafless matured stems that are two or three years old. Each inflorescence carries 2-3 (-6) flowers that are 4-6 (-8) cm across. The long-lived flowers last for more than 4 weeks.
Variable in colour, the flowers of Den.
heterocarpum have white, pale creamy-yellow to amber segments with a yellow
disc on the lip. There are also maroon, crimson or brown venations on the
side-lobes and base of the mid-lobe of the hairy or velvety lip. The margins of
the lip mid-lobe are often recurved with the apex also reflexed. Long-lived, the
flowers have a strong perfume that Lindley (1844) described as "something
intermediate between violets and primroses". Others have described the
scent as foetid or unpleasant.
John Lindley described fma. pallidum in the Botanical Register in 1839. It has a white lip except for a yellow stain at the base. Other forms that have been described in the literature include fma. album, which has pure white flowers and fma. aurantiacum that has rich orange-yellow blooms.
Its long-lived flowers are sweetly
fragrant; however some of the plants from the
Den.
heterocarpum is a widespread and variable species
that is currently understood to be distributed from Sri Lanka,
Good air circulation, 70% shade and a
well-drained potting medium are some of the cultural requirements of Den.
heterocarpum. Use a small pot, water and fertilise regularly when it is in
active growth. Tall or long plants may become top-heavy so a hanging pot or
basket may be more practical. Long-stemmed plants that tend to grow pendently
are best allowed to hang. Cease fertilising and reduce watering as the growths
mature in late autumn and provide with a cooler drier rest. Flowering occurs on
the older leafless growths and the newly produced growths usually shed their
leaves during the next season. I would recommend a winter minimum of 12 oC
but plants will tolerate lower temperatures for short periods if they are dry at
night.