Dendrobium bigibbum
Dendrobium bigibbum, commonly known as Cooktown orchid or mauve butterfly orchid, is an epiphytic or lithophytic orchid in the family Orchidaceae. It has cylindrical pseudobulbs, each with between three and five green or purplish leaves and arching flowering stems with up to twenty, usually lilac-purple flowers. It occurs in tropical North Queensland, Australia and New Guinea.
Description
Dendrobium bigibbum is an epiphytic or lithophytic orchid with green or purplish pseudobulbs long and wide, often with purplish edges. Each pseudobulb has between three and five egg-shaped leaves long and wide. The arching flowering stems are long with between two and twenty lilac-purple, rarely bluish or pinkish flowers. The flowers are resupinate, long and wide, the size depending on the variety. The sepals are oblong to egg-shaped, long and wide. The dorsal sepal is upright or turned back and the lateral sepals spread widely apart from each other. The petals are broadly egg-shaped, long and wide. The labellum is long, wide and has three lobes. The side lobes are upright and the middle lobe has four or five ridges along its midline and a hairy patch in the middle. Flowering occurs from February to July.Taxonomy and naming
Dendrobium bigibbum was first formally described in 1852 by John Lindley and the description was published in Paxton's Flower Garden.Four varieties of this species are recognised by the Plants of the World Online, but not by the Australian Plant Census, which lists them as synonyms of D. bigibbum:
- Dendrobium bigibbum var. bigibbum, the mauve butterfly orchid, that has a white spot in the centre of the labellum and occurs at low altitudes on Cape York Peninsula, some Torres Strait Islands and southern New Guinea;
- Dendrobium bigibbum var. compactum, Peter B.Adams a lithophyte with a narrow distribution at an elevation of in the wet tropics;
- Dendrobium bigibbum var. schoederianum Peter B.Adams that has variably coloured flowers and only grows on Larat Island in the Tanimbar group;
- Dendrobium bigibbum var. superbum, Rchb.f. the Cooktown orchid, that has the largest flowers in the group but which lack the white spot in the centre of the labellum and occurs between Cooktown and Mount Molloy.
Queensland State Floral Emblem
The Queensland government, in preparation for its 1959 Centenary, sought advice as to what native species would be a good floral emblem. Specifically, the government was looking for an easily grown species found only in Queensland, which was decorative, distinctive, and close to the State colour, maroon. The Cooktown orchid, which meets these criteria, was one of the four initial suggestions, the others being the red silky oak, the umbrella tree, and the wheel-of-fire. The Courier-Mail, a Brisbane newspaper, sought additional suggestions from its readers, and compiled a list of 13 possibilities. In a public poll, the Cooktown orchid came in first place, the red silky oak in second, and poinsettia, already the floral emblem of the capital city Brisbane, came in third.In 1968 the Cooktown orchid was featured on an Australian postage stamp.