The Confusing Australian Dendrobiums Charles Ford

Charles needs no introduction having been a member of the society for more years than he probably cares to remember. Recent lifestyle changes have led to spending a lot of time in Sydney, Australia alongside wife JJ who is currently working down under. It’s a hard life, but someone has to do it… Being retired, once he has done the housework, he is able to take in the local flora, both in Sydney and the surrounding areas. Lots of orchids are native to Australia, but not necessarily around Sydney. Many are native to other areas of the country, and have been introduced and flourished, but it is the native Dendrobiums that are the focus of this lecture. This isn’t a scientific review, more an attempt to clarify some things. The Dendrobiums of Australia are confined to the east coast, and more so in the north east as well as the western side of Cape York. kingianum is one of the most common species, and is definitely one where confusion reigns, and has done so for a very long time. Many believe that it may be a natural hybrid, and that this is supported by size variants. speciosum grows to a huge size around Sydney, but smaller elsewhere. Perhaps trying to understand just what a species is, what is a subspecies/variety, and where does the role of evolution actually fit in.

Australia is a huge country that has undergone huge vegetative changes over the last million years. It is currently a mainly dry country with a green coast. The eastern coast is warmer and wetter, and therefore greener with the Great Dividing Range generating varying degrees of forest. The last ice age, and transition to the current climate has provided the current range of/within species. It is quite probable that up to 90% of species were lost during the ice age, and we may have lost many wonderful species. Evidence of this can be seen with isolated groups of Cycads, and the Wollemi pine that survived in an isolated canyon, but couldn’t re-establish countrywide as it was locked in by miles of desert. Many orchid species come from an isolated or relatively few habitats, and as such are standard, and consistent in reproduction. kingianum is a multi-sited species along the whole of the east coast. It is bigger in the north, and smaller in the south, as dictated by the climatic differences. It is therefore a species complex. The same is true of speciosum where Ssp. pendunculatum is quite small to Ssp. speciosum is huge. They are mainly epiphytes, but will also grow on rocks. The choice of trees is quite noticeable. Eucalyptus is the noted Australian tree, but won’t support orchids due to its habit of shedding its bark. Figs and ironbarks are the favourite, with figs especially having many nooks and crannies for the roots to cling to. They are quite adaptable, and can be seen growing in cinder block walls In Sydney speciosum ssp. speciosum is known as the Sydney Rock Lily, and is often seen as a lithophyte. Flowers are white to yellow. Ssp. hillii is found to the north of Sydney in the rainforest – all 3 tiers of it. It grows over 1m tall. It grows into large clumps – both size and weight, and will break off and survive on the floor. Flowers are white to ivory. Ssp. grandiflorum is further north in the Blackdown hills, and has stunning fragrant yellow flowers up to 4” across with pseudobulbs of 1m. Ssp. capricornicum has become isolated from the other subspecies growing on the eastern slopes of a volcanic plug which is the more moist side. Ssp. pendunculatum is the more northerly and grows in a drier climate. The vegetation is quite sparse, almost desert with grass trees. Small is the key to survival, and the psuedobulbs are 2-3”, with fairly long pendant spikes. There are several subspecies of kingianum, with most varying in size north to south, with various colour forms from red to white. kingianum ssp. carnarvonense comes from the Carnarvon Gorge, and is isolated from the remaining species by miles of desert, but is still similar. A close relative to the Dendrobiums are the Dockrillas. They vary mainly in having narrowly terete leaves and a narrow flexible stem that doesn’t really support the plant. They grow up in the canopy of fig trees, and have very fleshy thick roots. The Australians tend to be splitters rather than lumpers, and jump at the chance to define new species, subspecies or variants, even when they share the same DNA. A step too far! At the start Charles said that these are confusing species, and that confusion breeds more confusion. We are now a little clearer – aren’t we? Thank You Charles.