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The type specimen of Dendrobium foelschei is from Port Darwin, and it is broadly the form that extends across the Northern Territory and parts of the Kimberley in Western Australia. Dendrobium foelschei also exists on the northern and north-western side of Cape York (discussed separately here as it may be a slightly different botanical variety). It is unclear whether Dendrobium occurs anywhere in the Gulf of Carpentaria however if it does, it would seem likely to be Dendrobium foelschei. Furthermore, Clem and Jones (2002) report that this variety occurs on the Torres Strait Islands and in New Guinea. Other sources have confirmed to me that Dendrobium foelshei does occur into the Torres Strait and New Guinea. A plant shown on the Orchids of New Guinea website resource as Dendrobium canaliculatum (cultivated in Port Moresby and not given a location of collection) displays foelschei features without appearing entirely like a typical NT/WA plant (notably photos can be very hard to use to accurately identify plants).
Dendrobium foelschei was originally described as a separate species however has in recent decades mostly been described as a variety of Dendrobium canaliculatum. It was always recognised as the most distinct of the Dendrobium canaliculatum group.
I am now convinced it constitutes a separate species and future scientific publications will confirm this (notwithstanding the existing separation by M.A.Clem. & D.L.Jones, Orchadian 13(11): 486 (2002)). Evidence for separation as a distinct species has been provided in discussion with others working on this group of orchids and supported by my own observations and includes:
The most obvious characteristic of Dendrobium foelschei compared to Dendrobium canaliculatum is the generally pendulous raceme and pendulous and often cupped flowers. However it differs across a number of other characteristics (which are more important to its distinction). This species is rather rare in cultivation in part due to its often rather poor floral characteristics compared to Dendrobium canaliculatum and in part due to its distribution being from where few orchids are collected.
I have never seen wild Northern Territory or Western Australian plants however they are reported to grow in the typical areas on Melaleuca’s (particularly Melaleuca viridiflora) as well as Freshwater Mangrove (Barringtonia acutangula).
Vegetatively, Dendrobium foelschei is distinguishable from Dendrobium canaliculutum by typically narrower pseudobulbs and longer, narrower and more terete leaves. If typical Dendrobium canaliculatum often resembles an onion, Dendrobium foelschei could be described as more resembling a shallot! In colour, the bulbs and leaves are similar to Dendrobium canaliculatum var. canaliculatum with dark edges often on the leaves and dark striations on the bulbs. Leaves are often an olive to blueish grey colour. Please note with all the vegetative features that considerable variation occurs between plants depending on their growing conditions. So, for example, some plants of Dendrobium foelshei may appear generally as Dendrobium canaliculatum (broader greener leaves, larger, thicker bulbs) and vice versa. However if comparing many plants of two populations grown in similar conditions, the differences outlined between the varieties are clear.
Typical leaf form, from left to right: Dendrobium foelschei; Dendrobium foelschei (Queensland); Dendrobium canaliculatum var canaliculatum; Dendrobium canaliculatum var tattonianum
Flowers of Dendrobium foelschei are most notable for being pendulous, that is, they hang loosely from the raceme looking at the ground. The racemes (flower spikes) of foelschei are also often arching to pendulous, whereas those of canaliculatum almost always try to point straight for the sky. Generally, it is noticeably when the plants are side-by-side that the flower spikes on Dendrobium foelschei are much thinner than the Dendrobium canaliculatum - and hence it flops over when the flowers get weighty. Also, the developing flowering buds of Dendrobium foelschei are different in shape to Dendrobium canaliculatum, having an overly 'crooked' shape looking somewhat like a flamingo's beak. The flowers themselves are rather large (larger on average than Dendrobium canaliculatum) however the petals and sepals are narrow and the flowers cupped (poorly opening) meaning they don't necessarily look large. The structure of the racemes and flowers means this variety does not present very well at all - although some plants are quite reasonable (and it seems to me that on average Queensland plants are better presented than NT/WA forms). Although they do open up and enlarge over a long time period - several weeks - and so presentation does improve over the lifespan of the flowers and they are at their best in their final weeks. And the flowers last a surprisingly long time despite there apparently poor substance. Indeed, without having ever recorded the exact lengths, I would confidently say Dendrobium foelschei blooms last longer than either variety of Dendrobium canaliculatum.
Dendrobium foelschei presents some colours – interesting greys and purplish shades – which are completely absent in Dendrobium canaliculatum . Other colours – browns, tans, yellows and greens are also reported to occur. The basal colour of the flowers is off-white. The labellum is also distinct – it is narrower and more tightly ‘rolled’ and the ridges on the lip callus are far more pronounced than Dendrobium canaliculatum. The labellum with its very high ridges almost gives the appearance of a tuft of hairs on some plants, or three very high keels on others. Predominant colouring on the labellum is purple on a white to yellowish base.
The easiest way to distinguish Dendrobium foelschei from Dendrobium canaliculatum is to turn the flower over and look at the underside of the labellum. In Dendrobium foelschei the middle of the labellum is distinctly narrowed, resulting in a what looks a bit like a spoon or spade with its handle.
Underside of Dendrobium foelschei labellum with the narrow middle labellum circled
Left to right: Dendrobium canaliculatum var tattonianum; Dendrobium canaliculatum var canaliculatum: Dendrobium foelschei; Dendrobium foelschei (Queensland)
Left to right: Dendrobium foelschei; Dendrobium foelschei (Queensland); Dendrobium canaliculatum var canaliculatum; Dendrobium canaliculatum var tattonianum
It seems that some of the few plants in cultivation are the QLD form of Dendrobium foelschei rather than the NT or Kimberley variety. Whilst I have it from better authority that the Queensland plants are Dendrobium foelschei (discussed separately here) – they are also seemingly somewhat different from the NT/WA plants (generally better presented, thicker spikes and cream to yellow colouration - no brown, grey, tan or purple). At this point, I only feel comfortable calling NT and WA originated plants as type Dendrobium foelschei whilst recognising this caution may be shown to be unwarranted. I do feel that at best the Queensland plants are a botanical variety of Dendrobium foelschei or otherwise simply a regional colour form.
I only have several 'true' Dendrobium foelschei (from NT or WA) as well as some recently deflasked seedlings of uncertain origin. Whilst I will always maintain this variety for botanical interest, I also hope to learn more about the variation in the variety and any horticulturally superior clones that may exist. As this variety of so uncommon in cultivation, and so little has been written about it, I have no idea as to what the best plants look like, or what is the full variation of colour. The variety has a large natural range, and some surprising plants are likely to occur. Discussion with those more experienced with Dendrobium foelschei across its range confirm that some horticulturally excellent individual plants do occur (they are not all cupped flowers on pendulous spikes).
I would not be surprised if this species has not been utilised in hybridising at all to date. It has some unique colours and features, and it is simply not known how it will contribute as a parent. Dendrobium carronii was until relatively recently also considered a form of Dendrobium canaliculatum. It performs quite differently in hybrids to Dendrobium canaliculatum and likely Dendrobium foelschei will be different again.
Into the near future I do intend to flask a quantity of this species to grow on and observe the variation. I also intend to try some hybrids to start to understand how it behaves as a parent. At some point I also hope I will get a chance to observe flowering wild plants in their natural habitat.
A more scientific description of Dendrobium foelschei (as Cepobaculum foelschei) adapted from M.A.Clem. & D.L.Jones, Orchadian 13(11): 486 (2002) can be accessed from the Australian Tropical Rainforest Orchids website by following this LINK.