Dendrobium speciosum
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.
Name: Dendrobium speciosum Sm., Exotic Bot. 1: 17,t. 10(1804).
Synonym: Thelychiton speciosa (Sm.) M.A.Clem. & D.L.Jones (pars)
Dendrobium speciosum was discovered at Port Jackson in 1880 but was first described in England by 1804 by Sir James Edward Smith from a specimen sent to him by Surgeon General J. White. It grows east of the Great Divide from Cooktown in far north Queensland to Genoa in Victoria near the NSW border.
Common names: King orchid, rock orchid
As the name suggests, this is the king of Australian epiphytic orchids and deservedly so. It grows into large clumps, sometimes entirely encircling the trunk of its host tree. The canes can be up to 1m long, and the racemes up to 60cm long bearing scores of small creamy-yellow flowers, each about 30mm across. The plant also occur on cliffs and on the ground on rocky outcrops, also growing into large clumps when allowed to.
Locally they tend to colonise brush box trees in the wet sclerophyll forest, and strangler figs and other large trees in the rainforest.
There are a number of King Orchid species, subspecies, and varieties but in our area the plant commonly referred to as "King Orchid" is either D. speciosum var. hillii or D. speciosum var. grandiflorum. A table showing the current nomenclature and synonyms is presented at the end of this article.
Dendrobium speciosum var. hillii Masters
This variety has a range from south of the Hawkesbury River in NSW through to near Crow’s Nest in Southern Queensland. Typically the plants can be very large with pseudobulbs up to 75cm tall. Racemes are variable up to 70cm long and with up to 250 flowers that are mostly small and white to cream in colour. They may be well spaced on the raceme or densely packed. In its typical form var. hillii has numerous upright roots up to 30cms through the plant mass, which effectively act as a litter trap.
Dendrobium speciosum var. grandiflorum
This variety ranges from the Mt Mee - Crow’s Nest area to Mt Morgan and inland to Monto and Cania Gorge. Its southern range overlaps with that of var. hillii where the flowers are smaller. This species is very variable with long pseudobulbs up to 95cm with racemes of up to 150 flowers that are sparse to densely clustered. The flowers are small to some of the largest in the species, pale yellow to deep golden in colour.
Hybridisation
Dendrobium speciosum in the wild is known to hybridise with a number of other native dendrobiums in particular D. kingianum (Den. X delicatum) and D. gracilicaule (Den. X gracillimum). Both of the other two species are a common component in flora of our region. However selective breeding programs have produced show bench quality plants.
Without doubt, this species is the most important parent in the breeding of Australian native hybrids. Some of these are illustrated below.
Dendrobium X delicatum occurs from the Hunter River in central - eastern NSW to the Blackall Ranges in SE Queensland. It grows on rocks or cliff faces in open forest country of the ranges but is quite rare. It is a hybrid between D. speciosum var. hillii and D. kingianum.
Dendrobium X gracillimum is a hybrid between D. speciosum var. hillii and D. gracilicaule. This hybrid is also uncommon but widespread in the wild and occurs from near Maleny in SE Queensland and Wauchope in NSW. It has a preference for rainforest trees on the ranges at moderately low altitudes.
Aboriginal usage
Stems were beaten to a pulp to break up the fibre before being cooked on hot stones. The starch can then be washed out. The starch can also be used to fix paints.
