Dendrobium tetragonum Cunn.
This article was written in 2020 and is part of our Wayne Harris Article Series. Wayne was an avid orchid-enthusiast, photographer, author of several orchid publications and life-member of the Nambour Orchid Society. After a short illness, Wayne sadly passed away in 2020.
Allan Cunningham (Botanist & explorer) collected the holotype of this species from Moreton Bay in June 1828. He described it as “an epiphyte hanging loosely from the stems of small trees in dry shaded woods, Moreton Bay”
In this article I will discuss the two varieties which can be found in our region as well as the well known form from North Queensland. The type form of the species var. tetragonum is a widespread and common plant extending from Fraser Island to near Tomerong just west of Jervis Bay, NSW. It is found from coastal lowlands through to about 1200m and particularly along streams. Flowers are about 30-45mm x 20-40mm, greenish to yellowish with a dark red/brown marginal band. The form illustrated here is a particularly colourful plant.
Dendrobium tetragonum var. melaleucaphilum ranges from the Blackdown Tablelan through to the Blue Mountains in NSW up to about 450m. It is locally common occurring as an epiphtye but occasionally is found on rocks. It prefers sheltered environments particularly near streams. It commonly is found on paperbark trees in swamps near the coast. Flowers are about 60-80mm x 20-40mm greenish to greenish yellow with occasional red markings. Mid lobe of labellum is broad when flattened.
Dendrobium tetragonum var. giganteum is a form which can occasionally be seen on our show benches. Its range is from the Iron Range on Cape York to Mackay. It is locally common and can be found on trees in the shade beside streams. Flowers are about 70-120mm x 60-80mm and are greenish-yellow with prominent red markings. The mid lobe of the labellum is much narrower than the lateral lobes when flattened.
There are 2 or 3 other forms that have been described but are rarely seen. Perhaps the exception is var. cacatua which is a very pale form with few if any red markings. All forms of the species are easily grown in the bush house and are best mounted and watered frequently throughout the year. Pot culture can be successful also.