Dendrobium canaliculatum var. pallidum
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Dendrobium canaliculatum var. pallidum is described from a plant collected at Starcke River (Cape York Peninsula) in 1954. It is described as similar to the type variety however with pale yellow to greenish petals and sepals and a white labellum.
I am aware of rarely occurring plants fitting the description of var. pallidum having been found from across the range of var. tattonianum and var. canaliculatum. I have one in my collection of uncertain origin, although in plant and flower form almost certainly var. canaliculatum.
Starke River is north of Cooktown, east of Laura and Lakefield National Park and south of Cape Melville. This is var. canaliculatum country at the northern limits of where some features of var. tattonianum can sometimes be detected. I am not aware of any reports of a population of pale Tea Tree Orchids occurring in this area and if it did, it would be surrounded by classic var. canaliculatum. Nothing to suggest a definable separate clade of Tea Tree Orchids.
It seems most likely to me that the plant described as Dendrobium canaliculatum var. pallidum is a natural variation of Dendrobium canaliculatum where a particular colour gene for the flowers is missing or altered so as not to be expressed. Some call these plants lutinos or albas (though true albas have no colour expression whatsoever). This is a well-known phenomena in many other orchid species – a classic example is Dendrobium discolor with the pure yellow form var. broomfieldii occurring randomly and uncommonly across its range.
Hence, I do not consider Dendrobium canaliculatum var. pallidum to be a true variety (i.e. a population/clade within the species that is defined by coherently distinct morphological features and geographic and/or habit range). Indeed, I do not consider similar plants of other species as varieties either – the term Dendrobium discolor forma broomfieldii is more appropriate for example. A form or forma has a distinct morphological feature but is not otherwise separated from a broader population of the species.
Back to the plant of this form that I have in my collection, to name it as a distinct I would consider Dendrobium canaliculatum var. canaliculatum forma pallidum as appropriate. Something of a mouthful that one!