Diuris amplissima

Diuris amplissima, commonly called the giant donkey orchid is a species of orchid that is endemic to the south-west of Western Australia. It is a rare species and the largest Diuris in Western Australia. It has two or three leaves at its base and up to seven purple and dull yellowish-brown flowers on a tall flowering stem.

Description
Diuris amplissima is a tuberous, perennial herb, usually growing to a height of  with two or three leaves emerging at the base, each leaf  long and  wide. There are between three and seven purple and dull yellowish-brown flowers  long and  wide. The dorsal sepal is erect,  long and  wide and oval to kidney-shaped (wider than long). The lateral sepals are linear to sword-shaped, green with purplish marks,  long,  wide, turned downwards and usually parallel to each other. The petals are more or less erect with an elliptic to oval blade  long and  wide on a purplish-brown stalk  long. The labellum is  long and has three lobes. The centre lobe is wedge-shaped,  long,  wide and the side lobes are asymmetric egg-shaped,  long and  wide with wavy or crinkled edges. There is a ridge-like callus  in the mid-line of the base of the labellum. Flowering occurs from September to November.

Taxonomy and naming
Diuris amplissima was first formally described in 1991 by David Jones from a specimen collected near Moodiarrup, and the description was published in Australian Orchid Review. The specific epithet (amplissima) is a Latin word meaning "largest", referring to the "impressive flowers".

Distribution and habitat
The giant donkey orchid grows in woodland and forest between Porongurup and Capel in the Avon Wheatbelt, Jarrah Forest and Mallee biogeographic regions. It is a rare species, similar to D. magnifica but grows in heavier soils than the sandy habitat of that species.

Conservation
Diuris amplissima is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.

References 

amplissima
Category:Endemic orchids of Australia
Category:Orchids of Western Australia
Category:Endemic flora of Western Australia
Category:Plants described in 1991