Australian Floral Emblems - Dendrobium bigibbum

Dendrobium bigibbum (the "Cooktown Orchid") is the floral emblem of Queensland and is probably the best known and most colourful of Australia's orchid species. Dendrobium is a large genus with around 1400 species spread throughout Asia and the Pacific. Australia has about 56 species. Like most Dendrobiums, D.bigibbum is an epiphytic orchid which means that it grows on the trunks and branches of trees and has no contact with the ground. The name "Dendrobium" reflects the epiphytic nature of the species and comes from the Greek dendron, a tree, and bios, life (ie living on trees).

Epiphytes receive nutrients through the break down of leaf litter that accumulates around their root systems. The plants are not parasitic - they only depend on the tree for support and do not penetrate the tree's tissues to extract water and nutrients. The tree, however, does not appear to gain any benefit from having the orchids attached; ie. the benefits are solely to the orchids and there is no symbiosis involved.

D.bigibbum occurs in the forests of Queensland north from around Cooktown and it is common on the Cape York Peninsular and the islands of Torres Strait. In nature it hybridises with D.discolor. The purple flowers are borne on long, terminal racemes and there may be as many as ten flowers on each raceme. Flowers are large, being up to 65 mm in diameter. Occasionally white flowered forms are seen.

The large, purple flowers of Dendrobium bigibbum make this a very spectacular species which is very popular in cultivation. Select the thumbnail image or plant name for a higher resolution image (17k).

The "Cooktown Orchid" has been cultivated for many years by orchid enthusiasts and has been used in hybridisation work with other Australian and exotic "hard cane" Dendrobiums. It grows fairly easily in cultivation in sub-tropical and tropical areas where cultivation in a bush house is adequate. In temperate districts the plant requires a heated glasshouse although it can be flowered (with luck!), in temperate coastal areas in a very warm bush house. Plants can usually be obtained through specialist orchid breeders.

The specific name "bigibbum" has nothing whatever to do with human anatomy! It means "2-humped" and refers to the shape of the spur, a floral structure.

Australian Plants online - September 1996
The Society for Growing Australian Plants