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:


​Supported Varieties

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. canaliculatum


  • Cape York Peninsula, north of about the Palmer and Bloomfield rivers to the Torres Strait Islands and New Guinea.
  • Green to grey-green leaves, often dark margins on leaves and dark striations on sheaths on the pseudobulbs.
  • Flowers from almost black, brown to oranges, yellows and  orche reds on tips, fades to off-white to yellowish to brownish basal colouration.
  • Labellum with usually small purple disk, also red and yellow markings.


                                                                                


 Dendrobium canaliculatum var.  tattonianum


  • Rockhampton area north to about Cairns and the Daintree.
  • Green leaves, slightly broader than other varieties. No dark margins or striations except in intergraded populations with var. canaliculatum.
  • Flowers yellow on tips, cuts abruptly to pure white basal colouration. Labellum with large puple disk and purple markings, no other colours.



                                                                                                    

                                                                       

     (Dendrobium canaliculatum var. nigrescens)

 Dendrobium canaliculatum var. tattonianum

  • Originally described from Port Douglas plants.
  • Generally similar to var. tattonianum with brownish tips to the petals and sepals and often some red on the labellum.
  • Colour form where var. tattonianum intergrades with var. canaliculatum. Personally consider them most consistent with var. tattonianum but this distinction is speculative and of minimal practical value. 


                                                                                


     (Dendrobium canaliculatum var. pallidum)

 Dendrobium canaliculatum forma pallidum

  • Originally described from Starke River (Cape Melville) plants.
  • Yellowish to greenish flower, white and/or yellow labellum with no purple or red.
  • Plants consistent with the description have been found across the species range.
  • Spontaneous colour form due to absence of a colour gene (lutino form).


     

         (Dendrobium canaliculatum (New Guinea))

     Dendrobium canaliculatum var. canaliculatum (New Guinea)

     Dendrobium foelschei (New Guinea)

    Dendrobium canaliculatum var. ?


    • Minimal detailed information available.
    • ​Attributed photos to New Guinea suggest Dendrobium foelschei (or similar).
    • Credible source has indicated to me that Dendrobium foelschei and Dendrobium canaliculatum var. canaliculatum (or similar to these) occur in New Guinea.
    • Poorly studied area similarities / differences to Australia plants not characterised.
    • Possibility of additional variety/s due to poorly studied area (though I have found no evidence of this).