There is no authoritative, widely accepted categorisation of the Dendrobium canaliculatum complex. Credible sources vary in approaches including one species (no varieties); one species (five varieties), or three species (no varieties). They may be in the genus Dendrobium or a new genus Cepobaculum.
This confusion is common across the orchid world and to some degree reflects the difficulty of classifying populations of plants that have no regard for human ideas of how species and varieties should segregate. Most Australian orchid enthusiasts would be familiar with the ongoing saga with the classification of the Dendrobium (Thelychiton?) speciosum complex – although with this species there now seems to be a general agreement (at least in the orchid growing community) with the conclusions in the 2006 Adams, Burke and Lawson paper (follow this link to a PDF copy hosted by Bill Dobson on his personal Dendrobium speciosum website). One senses the need for a PhD or three and some thorough field and scientific work yet to be done before a consensus can be formed for the Dendrobium canaliculatum complex to be sorted into a generally accepted nomenclature.
Whilst there remains considerable debate and uncertainty regarding the classification of Tea Tree Orchids, amateur growers continue to form their own opinions. As do I. My thoughts on the classification of Dendrobium canaliculatum are formed from extensive reading of others work (scientific and amateur), the observation of thousands of plants in the wild and the cultivation of quite a few as well.
Uncharacteristically, I find my observations align most closely to M.A.Clem. & D.L.Jones, Orchadian 13(11): 486 (2002) – though with several significant qualifications. Like most growers I don’t like much of what Clem & Jones propose with Australian Dendrobiums and find some of their distinctions of new genus and especially separate species frankly unfathomable. For canaliculatum I can’t personally buy into the new genus (Cepobaculum) nor necessarily the three distinct species they create from the canaliculatum complex (within Cepobaculum). Yet the distinctions made between the three types (species in their work) matches my observations very well, with the physical characteristics and distribution specified by Clem & Jones also consider most reasonable. The differentiation of Dendrobium foelschei as a species I now support based on field, morphological and preliminary genetic work (the description of this species is now in Other 'Tea Tree' Orchid Species). Lastly, I have also added some further differentiation and observation of intergrading of forms to that published by Clem & Jones.
A summary table of the two varieties of Dendrobium canaliculatum that I see as clearly recognisable (and mostly aligning with the two species of Cepobaculum of M.A.Clem. & D.L.Jones, Orchadian 13(11): 486 (2002) minus Dendrobium foelschei) along with summary key features of each variety as I have observed follows:
Varieties of Tea Tree Orchid
Those varieties mentioned by various authors of which I am uncertain or don’t support are in the following table:
Unsupported and Uncertain Varieties
(Dendrobium canaliculatum var. nigrescens)
(Dendrobium canaliculatum var. pallidum)
(Dendrobium canaliculatum (New Guinea))
Dendrobium foelschei (New Guinea)
Dendrobium canaliculatum var. ?