ANOS Sydney April 2019 Plant of the Evening

Dendrobium bigibbum var. compactum

It was quite a young plant with 2 flowering spikes but only one of which carried fully open flowers. Being the time of the year for the flowering of this well-known and popular Australian species, there were about half a dozen plants of various varieties on the bench. This plant stood out amongst the others, some much larger and some with more flowers because of its superior floral shape, better habit (presentation of flowers) and intense colour of the flowers. There were 7 fully open flowers, all in excellent conditions, nicely arranged on the single raceme. The plant is grown in shade house with plenty of light and kept dry during winter months.

While this orchid has been classified as an individual species, namely Dendrobium lithocola, it is also commonly regarded as a variety of species Dendrobium bigibbum, i.e. Dendrobium bigibbum var. compactum, found in northern Australia. In the wild, this variety has very limited geographical distribution, grows on rocks south of Laura to Cairns on the eastern side of Cape York, Queensland. The flowers of Dendrobium bigibbum var. compactum are very similar to those of Dendrobium bigibbum var. superbum, another variety of this species. Apart from geographical distribution, its only distinguishing feature is the shortness of its pseudobulbs, usually less than 20 cm long.

This species including this variety has a long history of being used in hybridisation to improve the quality as well as the longevity of the flowers. As of early 2019, there are 629 first generation progenies (with the species as one of the parents) and 7,663 total progenies deriving from this species. It is the cornerstone in the hybridisation of the “hot-cold” dendrobium hybrids. Amongst the many desirable attributes of these hybrids are increased longevity of bloom, increased flowering period, increased flower size and more contrasting colours. Use of Dendrobium bigibbum var. compactum in breeding in particular can help to produce offspring with more compact habit.