Dendrobium sect. Rhizobium Lindl. was established by John Lindley in 1851 based on Den. linguiforme. This classification was used by Schlechter in his major revision of Dendrobium in 1911-14. Brieger proposed in 1981 that this group be separated as a new genus Dockrillia, but this was rejected at the time. Section Rhizobium includes around 30 species, which are mainly centered in Australia (17 –18 species) and New Guinea (10 species so far described), with others in New Caledonia, Fiji, Tahiti, Samoa, Aru Islands and Vanuatu. Like so many orchids, name changes have been common over the years – for example Den. striolatum Rchb.f. was described as Den. teretifolium (1839), Den. milliganii (1859) and Callista striolata (1891) (Clements 1989).
The species are very variable in leaf form and flowers, which are commonly non-resupinate, appearing upside down. This feature can also be seen in the other Dendrobium sections Conostalix and Lichenastrum. Plants are usually found at low to moderate altitudes, growing as epiphytes or lithophytes in rainforests and open forests, often in bright light. The brighter the light the redder the growths become, due to the presence of anthrocyanins.
There has been a rise in popularity of these cool growing plants in the past 20 years, and I feel that there is much potential for further work in hybridisation. The crucial work in these hybrids was done by Neil Finch, Phil Spence and Brian Gerhard in New South Wales, and more recent work by George Byrne-Dimos, Wayne Turville and Jeanne Dunn in Victoria.
Having acquired over 500 Rhizobium hybrids and species as part of the Down Under Native Orchids enterprise (DUNO) it was important to establish a new line of breeding, thus this article is a collection of my thoughts on previous results and future directions.. I reflect on hybrids I consider are ‘staples’ for future breeding and those that have made a substantial impact to date. I will also explore more recent hybrids that have proven their worth, and crosses made with