Diuris, commonly known as donkey orchids, is a genus of more than sixty species of flowering plants in the orchid family, Orchidaceae and is endemic to Australia apart from one species endemic to Timor. The name "Diuris" refers to the hanging sepals but the common name derives from the ear-like petals common to all species. All have mainly yellow flowers with darker markings and are thought to mimic nectar-producing flowers which open at the same time.
Orchids in the genus Diuris are terrestrial, perennial, deciduous, sympodial herbs, usually with a few inconspicuous, fine roots and one or two tubers lacking a protective sheath. The stem is short, erect and unbranched with a leaf-like cataphyll at each node. There are between one and ten grass-like leaves at the base of the plant.
The inflorescence is a raceme with a few to many brightly coloured, resupinate flowers on a wiry stalk. The dorsal sepal is shorter but wider than two lateral sepals and forms a hood over the column. The long, narrow, lateral sepals hang like a pair of tails below the labellum. The petals are different from the sepals, having a narrow base with the main part widely expanded, in the form of donkey ears. As is usual in orchids, one petal is highly modified as the central labellum, differing markedly from the other petals and sepals. The labellum has three distinct parts with the central part folded and the lateral parts arranged on either side of the column, often spreading widely, sometimes with a scalloped or wavy edge. The column is short with narrow wings. Flowering time depends on species but most species flower between September and November. One of the earliest to flower, D. brumalis flowers in June and D. emarginata sometimes flowers as late as January. The fruit which follows flowering is a thin-walled, dehiscent capsule containing up to 100 winged seeds.
Taxonomy and naming
The genus Diuris was first formally described in 1798 by James Edward Smith and the description was published in Transactions of the Linnean Society of London. Smith did not nominate a type species.
Distribution and habitat
Donkey orchids occur in all Australian states, but not the Northern Territory with one species (D. fryana) found in Timor. In New South Wales, most species grow among grasses in sclerophyll forest. In Western Australia, most grow in moist places such as coastal swamps or near granite outcrops. Donkey orchids usually grow as individual plants or in loose colonies and most occur at low altitudes, although D. monticola grows at up to 1,800 m (6,000 ft). Some species flower more profusely after fire and D. purdiei will only flower following a summer fire. In fire-prone areas, the tubers lie dormant in the soil and are not harmed by bushfires.
Donkey orchids are coloured like flowers that attract pollinating insects such as wasps, bees and flies but no Diuris produce nectar and very few have a scent. It is thought that Diuris species deceive insect by falsely advertising the presence of food and this hypothesis is supported by experiments on only one species, D. pardina.
The following species are listed in the Index Kewensis:
- Diuris abbreviata F.Muell. ex Benth 1873 (N.S.W., Qld.)
- Diuris aequalis F.Muell. ex Fitzg. 1876 (N.S.W.)
- Diuris alba R.Br. 1810 (N.S.W., Qld.)
- Diuris amplissima D.L.Jones 1991 (W.A.)
- Diuris arenaria D.L.Jones 1999 (N.S.W.)
- Diuris aurea Sm. 1804 (N.S.W., Qld.)
- Diuris basaltica D.L.Jones 2006 (Vic.)
- Diuris behrii Schltdl. 1847 (N.S.W., Vic., S.A.)
- Diuris bracteata Fitzg. 1891 (N.S.W.)
- Diuris brevifolia R.S.Rogers 1922 (N.S.W., S.A.)
- Diuris brevissima Fitzg. ex Nicholls 1942 (N.S.W.)
- Diuris brumalis D.L.Jones 1991 (W.A.)
- Diuris byronensis D.L.Jones 2003 (N.S.W.)
- Diuris callitrophila D.L.Jones 2003 (N.S.W.)
- Diuris carinata Lindl 1840 : tall bee orchid (W.A.)
- Diuris chrysantha D.L.Jones & M.A.Clem. 1987 (N.S.W., Qld.)
- Diuris chryseopsis D.L.Jones 1998 : snake orchid (N.S.W., Vic., Tas. S.A.)
- Diuris concinna D.L.Jones 1991 (W.A.)
- Diuris conspicillata D.L.Jones 1991 (W.A.)
- Diuris corymbosa Lindl. 1840 (W.A., S.A., Vic., N.S.W.)
- Diuris cuneata Fitzg. 1891 (N.S.W.)
- Diuris curta D.L.Jones 2006 (Qld.)
- Diuris curvifolia Lindl. 1840 (Tas.)
- Diuris disposita D.L.Jones 1991 (N.S.W.)
- Diuris drummondii Lindl. 1840 : tall donkey orchid (W.A.)
- Diuris eborensis D.L.Jones 2006 (N.S.W.)
- Diuris eburnea D.L.Jones 2006 (W.A.)
- Diuris emarginata R.Br. 1810 : tall donkey orchid
- Diuris emarginata var. emarginata (W.A.)
- Diuris emarginata var. pauciflora A.S.George 1971
- Diuris exitela D.L.Jones 1991 (Qld.)
- Diuris filifolia Lindl. 1840 : cat's face orchid (W.A.)
- Diuris flavescens D.L.Jones 1991 (N.S.W.)
- Diuris fragrantissima D.L.Jones & M.A.Clem. 1989 (Vic.)
- Diuris fryana Ridl. in H.O.Forbes 1885 (Timor)
- Diuris fucosa D.L.Jomes 2006 (N.S.W., Vic.)
- Diuris gregaria D.L.Jones 2006 (Vic.)
- Diuris hazeliae D.L.Jones 2013 (W.A.)
- Diuris heberlei D.L.Jones 1991 (W.A.)
- Diuris immaculata D.L.Jones 2006 (W.A.)
- Diuris insignis D.L.Jones & C.J.French 2013 (W.A.)
- Diuris jonesii C.J.French & G.Brockman 2013 (W.A.)
- Diuris laevis Fitzg. 1882 : nannygoat orchid (W.A.)
- Diuris lanceolata Lindl. 1840 (N.S.W., Vic., S.A., Tas.)
- Diuris laxiflora Lindl. 1840 : bee orchid (W.A.)
- Diuris longifolia R.Br. 1810 : purple pansy orchid or common donkey orchid (W.A.)
- Diuris luteola D.L.Jones & B.Gray 1991 (Qld.)
- Diuris maculata Sm. 1805 (Qld., N.S.W., Vic., S.A., Tas.)
- Diuris magnifica D.L.Jones 1991 (W.A.)
- Diuris micrantha D.L.Jones 1991 (W.A.)
- Diuris monticola D.L.Jones 1998 (N.S.W., Vic., Tas.)
- Diuris nigromontana D.L.Jones 2008 (A.C.T.)
- Diuris ochroma D.L.Jones 1994 (N.S.W., Vic.)
- Diuris oporina D.L.Jones 1991 (Qld.)
- Diuris orientis D.L.Jones 1998 (N.S.W., S.A., Vic., Tas.)
- Diuris palustris Lindl. 1840 (S.A., Vic., Tas.)
- Diuris pardina Lindl. 1840 (N.S.W., S.A., Vic., Tas.)
- Diuris parvipetala (Dockrill) D.L.Jones & M.A.Clem. 1987 (N.S.W., Qld.)
- Diuris pedunculata R.Br. 1810 (N.S.W., Vic.)
- Diuris perialla D.L.Jones & C.J.French 2012 (W.A.)
- Diuris picta J.Drumm. 1853 (W.A.)
- Diuris platichila Fitzg. 1891 (N.S.W.)
- Diuris praecox D.L.Jones 1991 (N.S.W.)
- Diuris protena D.L.Jones 2006 : northern golden moths (Vic.)
- Diuris pulchella D.L.Jones 1991 (W.A.)
- Diuris punctata Sm. 1804 : purple diuris (N.S.W., Qld., Vic.)
- Diuris punctata var. punctata
- Diuris punctata var. sulphurea Rupp 1944
- Diuris purdiei Diels 1903 : Purdie's donkey orchid (W.A.)
- Diuris recurva D.L.Jones 1991 (W.A.)
- Diuris refracta D.L.Jones & C.J.French 2013 (W.A.)
- Diuris secundiflora Fitzg. 1877 (N.S.W.)
- Diuris segregata D.L.Jones & C.J.French 2013 (W.A.)
- Diuris semilunulata Messmer in H.M.R.Rupp 1944 (N.S.W.)
- Diuris septentrionalis D.L.Jones & C.J.French 2013 (W.A.)
- Diuris setacea R.Br. 1910 : bristly donkey orchid (W.A.)
- Diuris striata Rupp 1944 (N.S.W.)
- Diuris subalpina D.L.Jones 2008 (N.S.W.)
- Diuris sulphurea R.Br. 1810 (N.S.W., Qld., S.A., Tas., Vic.)
- Diuris systena D.L.Jones & L.M.Copel. 2012 (N.S.W.)
- Diuris tinkeri D.L.Jones & C.J.French 2013 (W.A.)
- Diuris tricolor Fitzg. 1885 (N.S.W., Qld.)
- Diuris unica D.L.Jones 2006 (N.S.W., Qld.)
- Diuris venosa Rupp 1926 (N.S.W.)
- Diuris × fastidiosa R.S.Rogers 1927 (D. lanceolata × D. palustris)
- Diuris × nebulosa D.L.Jones 1991 (D. aurea × D. punctata)
- Diuris × palachila R.S.Rogers 1907 (D. behrii × D. pardina)
- Diuris × polymorpha Messmer in H.M.R.Rupp 1944 (D. lanceolata × D. platichila)
- Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia. (3rd ed.). Gooseberry Hill: Noel Hoffman. pp. 456–497. ISBN 9780646562322.
- Pridgeon (ed.), Alec M.; Cribb (ed.), Phillip J.; Chase (ed.), Mark W.; Rasmussen (ed.), Finn (2001). Genera Orchidacearum, Volume 2, Orchidoideae (part 1). Oxford, England: Oxford University Press. pp. 126–131. ISBN 0198507100.
- "Diuris". FloraBase. Western Australian Government Department of Parks and Wildlife.
- Jones, David L. "Genus Diuris". Royal Botanic Garden Sydney: plantnet. Retrieved 21 July 2016.
- "Diuris". APNI. Retrieved 21 July 2016.
- Smith, James Edward (1798). "The Characters of Twenty New Genera of Plants". Transactions of the Linnean Society of London. 4: 222. Retrieved 21 July 2016.
- Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press.
- Jones, David L. (1970). "Some thoughts on the taxonomy of the genus Diuris". Australasian Native Orchid Society.