Were it somehow possible to count every epiphytic (tree-growing) and lithophytic (rock-growing) orchid in Australia, I would confidently bet that the most abundant (by number of individuals) would be the little Tea Tree Orchid.
This orchid colonises a variety of habitats. I have seen plants growing on small scaly barked trees on ridgelines at an altitude of 650m near Townsville and on Burdekin Plum on ridgelines near the tip of Cape York. Between Cardwell and Cairns, in the near-impenetrable wet lowlands, they grow on the highest thin branches of tall Paperbarks (Melaleuca leucadendra) above the ephemeral watercourses. You will only ever see them on fallen branches, or for the sharp-eyed high in the tree-tops when in full flower. Surprising numbers can be sometimes found on fibrous-barked Angophora and Corymbia type Eucalypts, particularly along gullies and swampy watercourses. On the west coast of Cape York and the Northern Territory they grow on Freshwater Mangrove (Barringtonia acutangular). In the Macalister Range between Cairns and Port Douglas they receive lots of rain, and grow into large clumps particularly on Swamp Box trees (Lophostemon suaveolens) in both the gullies and on the sides of mountains. Some clumps here are the size of a toilet seat, and so leafy that at first glance they can be mistaken for Cymbidium canaliculatum.
Where this orchid absolutely dominates however is the extensive coastal forests of Broad-leaved Paperbark (Melaleuca viridiflora), a host which is common across this Orchid’s range. Indeed, almost anywhere in coastal Queensland north of Rockhampton where you can find a stand of mature Broad-leaved Paperbarks you will find Tea Tree Orchids. I understand it is much the same across the north of the Northern Territory, parts of the Kimberley and into southern New Guinea.
Broad-leaved Paperbark (Melaleuca viridiflora) flowers. Occasional plants have bright red flowers. Most stands of mature Broad-leaved Paperbark in coastal Northern Australia are host to colonies of Tea Tree Orchids.
The map below provides the distribution of the Tea Tree Orchid by its varieties (as I call them) in Australia. It is likely the distribution displayed is not complete, with the distribution in far Northern Australia in particular more extensive than shown.
Distribution of Dendrobium canaliculatum in Australia by variety. Variety canaliculatum and var. tattonianum intergrade (interbreed) around the Cairns area with features from apparent mixed parentage occasionally extending as far as Townsville in the south and Cape Melville in the North. On the tip of Cape York, the Torres Strait and New Guinea Dendrobium foelschei and Dendrobium canaliculatum var. canaliculatum do not intergrade despite populations occurring within close proximity.
The Tea Tree Orchid in the Wild
Melaleuca viridiflora forests cover millions of hectares across Northern Australia. Science has been published that finds that mature forests contain in the range of 150-500 tea trees per hectare. Commonly each mature tree will contain several Tea Tree Orchids per tree – some can have tens of individual orchids. And Dendrobium canaliculatum will also colonise other species of tree in these forests. Without attempting the math further from here, I get assure you that the little Tea Tree Orchid is a very abundant species!
In Australia, this orchid’s prevalence has led to its horticultural neglect. Wild clones in their thousands have come off farms, out of residential acreages, clearings for developments and undoubtedly from a few National Parks as well. Walk a few metres in the scrub by many places on Highway One between Rockhampton and Cairns and you could well trip over a few on the ground, still attached to fallen branches. Some of the new housing developments around Cairns, Townsville and Mackay take in prime habitat – each new house lot is probably another few dozen Dendrobium canaliculatum plants. The odd one is taken back to someone’s house.
Recently cleared Melaleuca viridiflora forest, presumably for beef cattle farming, just north of Laura (Cape York Peninsula). Consulting Google Earth with a back-of-the-envelope calculation reveals that this new paddock would have been home to many hundreds of thousands, or quite possibly millions, of Tea Tree Orchids. However much larger areas of suitable habitat remain preserved, and this orchid remains incredibly abundant across it's range.
In cultivation they are often left on the branches they are found, tied to living trees or shoved into pots of bark mix. Most die for various reasons, after perhaps a couple of years of persisting and flowering. But being so abundant many more are found from the bush to replace them.
I am neither a good nor prolific photographer (almost all the images on this site are taken with a smartphone) and so I have a disappointing collection of photos of the wild habitat of Dendrobium canaliculatum. I am steadily improving this situation however, and now there are a few images below to give an idea of how this species exists in the wild.
PLEASE CLICK ON THE BELOW IMAGE THUMBNAILS TO EXPAND AND VIEW
Typical Tea Tree Orchid habitats on Cape York Peninsula in the peak of the dry season. Melaleuca viridiflora dominates along with other species of Melaleuca and some unidentified species of short, scrubby trees. Hard to imagine from this image, but these forests will be green and boggy for the wet season and typically several months after (3-5 months per year). Habitat of Dendrobium canaliculatum var. canaliculatum and Dendrobium trilamellatum var. semifuscum
The habitat of Dendrobium canaliculatum can be extremely harsh. Fire has a very strong influence on the abundance of the species. In most forests, regular fires restrict the orchids to the tree tops - above the flames. In forests that receive regular 'cool' burns, or have minimal ground cover, orchids grow to within a a few metres of the ground. Some other forests with heavy undergrowth or irregular, 'hot' fires have very few or no orchids, despite being otherwise suitable as a habitat.
In contrast to the above, the below collection of images is a forest managed by traditional owners, who appear to achieve regular, 'cool' burns. Orchids grew to within 1.5 metres above the ground. The fire had only just passed, and a Dendrobium canaliculatum close to the ground had it's flowers wilted by the heat but was otherwise unscathed.
These stunted Tea Trees grow on a ridge line where there is too little undergrowth to support a significant fire. Despite the dry and hot position, Dendrobium canaliculatum was extremely abundant almost to ground level, including many seedlings.
Seemingly barren scrub at the head of a gully on a ridge was home to a large colony of Dendrobium canaliculatum with many seedlings. Again, a lack of fire due to the impoverished undergrowth has enabled this colony to grow thickly to near ground level, whereas in the more typical dense forests the orchids are only able to survive in the tree tops.
Below images are from a huge floodway area near sea level that appears to run shallow water for a number of months each year. A short sedge grows that doesn't appear to burn. The stunted trees, most the size of a backyard lemon tree, support large numbers of Dendrobium canaliculatum and Dendrobium trilamellatum var. semifuscum.
Dendrobium canaliculatum var. tattonianum in flower on a fallen Melaleuca viridiflora branch on the ground in the bush. Another can be seen in the background. Depending on fires, the orchids can persist several years on these fallen branches