|P. elatum (tall leek orchid) at Strettle Road Reserve Glen Forrest|
Prasophyllum commonly known as leek orchids, is a genus of about one hundred species of flowering plants in the orchid family, Orchidaceae and is found in Australia and New Zealand. The Australian species are found in all states but have not been recorded in the Northern Territory. The common name arises from their having a hollow, leek- or onion-like leaf. Some species only flower after summer fires and have flowers similar to those of Xanthorrhoea which flower at the same time, suggesting that they employ the same pollinating insects. Leek orchids are similar to those in the genus Genoplesium except that the free part of the leaf is cylindrical (flat in Genoplesium) and the labellum has a solid (rather than flexible) connection to the column. They range in size from the little laughing leek orchid (P. gracile) at about 15 cm (6 in) to the king leek orchid (P. regium) which grows up to 2 m (80 in) tall.
Orchids in the genus Prasophyllum are terrestrial, perennial, deciduous, sympodial herbs usually with a few inconspicuous, fine roots and a pair of more or less spherical tubers partly covered by a fibrous sheath. Replacement tubers form at the end of short root-like stolons. Leek orchids rarely reproduce by forming "daughter" tubers, relying on their flowers for reproduction. A single onion-like leaf develops near the base of the plant. The leaf is long, narrow, hollow, cylindrical and glabrous.
The inflorescence is a spike or raceme with a few to many non-resupinate flowers breaking through a thin part of the leaf. The dorsal sepal is wider than two lateral sepals which are often joined. The petals are often curved, shorter and narrower than the sepals. As is usual in orchids, one petal is highly modified as the central labellum, differing markedly from the other petals and sepals. The labellum is positioned above the column and rigidly attached to its base. It edges are usually wavy and rolled back. The labellum has a callus which consists of a raised, fleshy plate which is usually channelled, with the base forming an inverted basin shape. The sexual parts of the flower are fused to the column which is short and has narrow wings, often with a small lobe at the front. Leek orchids usually flower between late winter and early summer, depending on species, and the fruit that follows flowering is a non-fleshy, dehiscent capsule containing up to 500 seeds.
Taxonomy and naming
The genus Prasophyllum was first formally described by Robert Brown in 1810 and the description was published in Prodromus Florae Novae Hollandiae. Brown described twelve species but did not name a type species, however in 1989, Mark Clements nominated P. australe.
Distribution and habitat
Leek orchids occur in all states of Australia, but not in the Northern Territory. There are 20 named species in Western Australia as well as a further 40 that have been discovered but not as yet described. There are 28 species in Tasmania, about 40 in New South Wales  and 15 in South Australia. New Zealand has about 6 species, occurring on both main islands as well as Stewart and Chatham Islands. In Western Australia alone, they grow in a range of habitats from the margins of salt lakes, to swamps and dense Karri (Eucalyptus diversicolor) forests.
Many Western Australian species only flower after summer fires and in other years only produce leaves. Most flowers are strongly scented, produce nectar and are pollinated by insects but a few appear able to self-pollinated if not visited. They often have flowers similar to grass trees in the genus Xanthorrhoea, flower under similar conditions and are visited by a similar range of insects, suggesting that they mimic grass tree flowers.
There are about 100 currently accepted species as of May 2014.
- Prasophyllum affine Lindl. (1840)
- Prasophyllum album R.S.Rogers (1909)
- Prasophyllum alpestre D.L.Jones (1998)
- Prasophyllum amoenum D.L.Jones (1998)
- Prasophyllum antennatum M.A.Clem. & D.L.Jones (1989)
- Prasophyllum apoxychilum D.L.Jones (1998)
- Prasophyllum australe R.Br. (1810) southern leek orchid, Austral leek orchid
- Prasophyllum bagoense D.L.Jones (2000)
- Prasophyllum brevilabre (Lindl.) Hook.f. (1858)
- Prasophyllum brownii Rchb.f. (1871) Christmas leek orchid
- Prasophyllum buftonianum J.H.Willis (1953)
- Prasophyllum calcicola R.J.Bates (1989) limestone leek orchid
- Prasophyllum campestre R.J.Bates & D.L.Jones (1991)
- Prasophyllum canaliculatum D.L.Jones (1997)
- Prasophyllum candidum R.J.Bates & D.L.Jones (1991)
- Prasophyllum caricetum D.L.Jones (2000)
- Prasophyllum castaneum D.L.Jones (1998)
- Prasophyllum caudiculum D.L.Jones (2000)
- Prasophyllum colensoi Hook.f. (1853)
- Prasophyllum concinnum Nicholls (1948) trim leek orchid
- Prasophyllum constrictum R.S.Rogers (1909)
- Prasophyllum correctum D.L.Jones (1994)
- Prasophyllum crebriflorum D.L.Jones (2003)
- Prasophyllum cucullatum Rchb.f. (1871) hooded leek orchid
- Prasophyllum cyphochilum Benth. (1873) pouched leek orchid
- Prasophyllum diversiflorum Nicholls (1942) : gorae leek lrchid
- Prasophyllum dossenum R.J.Bates & D.L.Jones (1991)
- Prasophyllum drummondii Rchb.f. (1871) swamp leek orchid
- Prasophyllum elatum R.Br. tall leek orchid, piano orchid
- Prasophyllum exiguum Rupp (1948)
- Prasophyllum exile D.L.Jones & R.J.Bates (1991)
- Prasophyllum favonium D.L.Jones (1998)
- Prasophyllum fecundum R.J.Bates (1989)
- Prasophyllum fimbria Rchb.f. (1871) fringed leek orchid
- Prasophyllum fitzgeraldii R.S.Rogers & Maiden (1909)
- Prasophyllum flavum R.Br. (1810) yellow leek orchid
- Prasophyllum fosteri D.L.Jones (2000)
- Prasophyllum frenchii F.Muell. (1889) maroon leek orchid
- Prasophyllum fuscum R.Br. (1810) tailed leek orchid
- Prasophyllum gibbosum R.Br. (1810) humped leek orchid
- Prasophyllum giganteum Lindl. (1840) bronze leek orchid
- Prasophyllum goldsackii J.Z.Weber & R.J.Bates (1978)
- Prasophyllum gracillimum Nicholls (1948) slender leek orchid
- Prasophyllum hectori (Buchanan) Molloy, D.L.Jones & M.A.Clem (2005)
- Prasophyllum hians Rchb.f. (1871) yawning leek orchid
- Prasophyllum hygrophilum D.L.Jones & D.T.Rouse (2003)
- Prasophyllum incompositum D.L.Jones (1991)
- Prasophyllum incorrectum D.L.Jones (2003)
- Prasophyllum incurvum D.L.Jones (1998)
- Prasophyllum lanceolatum R.S.Rogers (1920)
- Prasophyllum lindleyanum Rchb.f. (1871) green leek orchid
- Prasophyllum litorale R.J.Bates (1990)
- Prasophyllum macrotys Lindl. (1840) inland Leek Orchid
- Prasophyllum milfordense D.L.Jones (1998)
- Prasophyllum mimulum D.L.Jones (2004)
- Prasophyllum mollissimum Rupp (1948)
- Prasophyllum montanum R.J.Bates & D.L.Jones (1991)
- Prasophyllum morganii Nicholls (1930) Cobungra leek orchid
- Prasophyllum mucronatum Rupp (1948)
- Prasophyllum murfetii D.L.Jones (2000)
- Prasophyllum nichollsianum Rupp (1942)
- Prasophyllum niphopedium D.L.Jones (2000)
- Prasophyllum nublingii R.S.Rogers (1927)
- Prasophyllum obovatum Rupp (1948)
- Prasophyllum occidentale R.S.Rogers (1908)
- Prasophyllum occultans R.J.Bates (1989)
- Prasophyllum odoratissimum D.L.Jones (1996)
- Prasophyllum odoratum R.S.Rogers (1909) scented leek orchid
- Prasophyllum olidum D.L.Jones (1998)
- Prasophyllum ovale Lindl. (1840) little leek orchid
- Prasophyllum pallens D.L.Jones (2000)
- Prasophyllum pallidum Nicholls (1933) pale leek orchid
- Prasophyllum parviflorum (R.S.Rogers) Nicholls (1941)
- Prasophyllum parvifolium Lindl. (1840) autumn leek orchid
- Prasophyllum patens R.Br. (1810) broad-lip leek orchid
- Prasophyllum paulinae D.L.Jones & M.A.Clem. (1996)
- Prasophyllum perangustum D.L.Jones (1998)
- Prasophyllum petilum D.L.Jones & R.J.Bates (1991)
- Prasophyllum plumiforme Fitzg. (1882)
- Prasophyllum pruinosum R.S.Rogers (1909)
- Prasophyllum pulchellum D.L.Jones (1998)
- Prasophyllum pyriforme E.Coleman (1932)
- Prasophyllum reflexum Fitzg. (1885)
- Prasophyllum regium R.S.Rogers (1918) king leek orchid
- Prasophyllum retroflexum D.L.Jones (2000)
- Prasophyllum robustum (Nicholls) M.A.Clem. & D.L.Jones (1989)
- Prasophyllum rogersii Rupp (1928) marsh leek orchid
- Prasophyllum rostratum Lindl. (1840) slaty leek orchid
- Prasophyllum sargentii (Nicholls) A.S.George (1971) frilled leek orchid
- Prasophyllum secutum D.L.Jones (1998)
- Prasophyllum solstitium D.L.Jones (2000)
- Prasophyllum sphacelatum D.L.Jones (1996)
- Prasophyllum spicatum R.J.Bates & D.L.Jones (1991)
- Prasophyllum stellatum D.L.Jones (1998)
- Prasophyllum striatum R.Br. (1810) streaked Leek Orchid
- Prasophyllum suaveolens D.L.Jones & R.J.Bates (1994)
- Prasophyllum subbisectum Nicholls (1936)
- Prasophyllum suttonii Ewart & B.Rees (1912) mauve leek orchid
- Prasophyllum sylvestre R.J.Bates & D.L.Jones (1991)
- Prasophyllum tadgellianum (R.S.Rogers) R.S.Rogers alpine leek orchid
- Prasophyllum taphanyx D.L.Jones (2004)
- Prasophyllum transversum Fitzg. (1891)
- Prasophyllum triangulare Fitzg. (1882) dark leek orchid
- Prasophyllum trifidum Rupp (1941)
- Prasophyllum truncatum Lindl. (1840)
- Prasophyllum tunbridgense D.L.Jones (1998)
- Prasophyllum unicum Rupp (1942)
- Prasophyllum validum R.S.Rogers (1927) green leek orchid
- Prasophyllum wallum R.J.Bates & D.L.Jones (1991)
- Prasophyllum wilkinsoniorum D.L.Jones (2000)
- Clements, Mark A. (1989). "Catalogue of Australian Orchidaceae". Australian Orchid Research. 1: 109.
- "Prasophyllum". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 11 July 2016.
- Jones, David L. (1998). "A Taxonomic Review of Prasophyllum R.Br. in Tasmania". Australian Orchid Research. 3: 94–134.
- Hoffman, Noel; Brown, Andrew (2011). Orchids of South-West Australia. (3rd ed.). Gooseberry Hill: Noel Hoffman. pp. 353–379. 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. 186–193. ISBN 0198507100.
- "Prasophyllum". FloraBase. Western Australian Government Department of Parks and Wildlife.
- Bernhardt, Peter H.; Rowe, Ross. "Genus Prasophyllum". Royal Botanic Garden Sydney: plantnet. Retrieved 11 July 2016.
- "Prasophyllum". APNI. Retrieved 11 July 2016.
- Brown, Robert (1810). Prodromus Florae Novae Hollandiae. London. p. 317. Retrieved 11 July 2016.
- Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press.
- "Prasophyllum". State Herbarium of South Australia: efloraSA. Retrieved 11 July 2016.
- "Prasophyllum". New Zealand Native Orchids; New Zealand Orchid Group. Retrieved 11 July 2016.
- Bates, Robert J.; Weber, Joseph Z. (1990). Orchids of South Australia. Adelaide, S. Aust.: Flora and Fauna of South Australia Handbook Committee. ISBN 0724365885.
- McQualter, Emily; Cross, Rob; McLean, Cassandra B.; Ladiges, Pauline Y. "Mycorrhizal fungi of Prasophyllum". Australian Government Department of the Environment and Water Resources. Retrieved 11 July 2016.
- Jones, D.L. & Clements, M.A. (2005). "Miscellaneous nomenclature notes and changes in Australian, New Guinea and New Zealand Orchidaceae". The Orchadian. 15 (1): 41.