Pterostylis
Image:Pterostylis metcalfei.001.jpg|thumb|right|Labelled diagram of Pterostylis metcalfei
[Image:Pterostylis coccinea 051002a.jpg|thumb|right|Pterostylis coccina, sepals and petals removed
(1) - labellum
(2) - hinge
(3) - stigma
(4) - pollinia]
Pterostylis is a genus of about 300 species of plants in the orchid family, Orchidaceae. Commonly called greenhood orchids, they are terrestrial, deciduous, perennial, tuberous, herbs found in Australia, New Zealand, New Guinea, New Caledonia and one Indonesian island. The flowers are mostly green, sometimes with brown, reddish or white stripes, and are distinguished from other orchids by their unusual flower structures and pollination mechanism.
Description
Greenhood orchids are all terrestrial herbs with an underground tuber like many other genera of orchids but are distinguished by a hood-like "galea" formed by the fusing of the dorsal sepal and two lateral petals. The galea curves forward, covers the sexual parts of the flower, is important in the pollination process and is about as long as the two petals. The dorsal sepal is translucent white with green, reddish or brown stripes. The two lateral sepals are joined at their base, form the front of the flower and usually protrude to form "points" or "ears" which extend above or to the side of the galea. The third petal forms the highly modified labellum. As in other orchids, the sexual parts of the flower form part of the column and in all greenhoods, this structure has a pair of mostly translucent wings and is also important in pollination.The tuber of a greenhood is usually more or less spherical in shape and lasts for about a year then dies. A new one is produced early in the life of the parent tuber at the same time as a new shoot is produced and continues to grow, reaching maturity at the end of the growing season. In some species, a larger number of "daughter" tubers grow, and a colony of orchids is produced. The leaves are either attached in a rosette to the base of the peduncle or "stalk" of the plant by a short petiole, or further up it, in which case the leaves are sessile. There may be one or several flowers on the peduncle.
The fruit of a greenhood is a dehiscent capsule containing up to 500 tiny seeds and is oblong to elliptic in shape with three ridges. Other parts of the flower wither soon after pollination and the dry remains are attached to the end of the capsule.
Taxonomy and naming
The first observation of Pterostylis by European botanists was probably by Joseph Banks when visited Botany Bay in 1770 but any specimens collected were lost later in the voyage. The first formal description of a greenhood was by Jacques Labillardière who collected a specimen from Bruny Island and gave it the name Disperis alata. After several name changes, Disperis alata is now known as Pterostylis alata. John White, the first surgeon-general of the colony of New South Wales collected several species and George Caley collected 208 greenhood specimens from 16 species and described them in great detail, including details of their habitat and gave them names like Druids Cap patersoni but did not publish his work.The genus Pterostylis was first raised by Robert Brown who formally described 19 species but did not nominate a type species. The species he described were collected from the east coast of the mainland and from Tasmania and the descriptions were published in Prodromus Florae Novae Hollandiae.
Alan Cunningham was the first to describe a New Zealand species, P. banksii and John Lindley described the first four Western Australian species, P. vittata, P. pyramidalis, P. barbata and P. scabra from specimens collected by James Drummond. About 300 species are recognised and about 200 of them have been formally described and named.
In 2001 the genus Pterostylis was split such that two new genera, Plumatichilos and Oligochaetochilus, were established based on morphological characters. These divisions effectively separated species with a thread-like, feathery labellum, and those with downward-curved lateral sepals from the remaining Pterostylis species. The following year, David Jones and Mark Clements proposed further separating Pterostylis into sixteen genera based on a combination of molecular and morphological characters: the genera Bunochilus, Crangonorchis, Diplodium, Eremorchis, Hymenochilus, Linguella, Oligochaetochilus, Petrorchis, Pharochilum, Plumatichilos, Ranorchis, Speculantha, Stamnorchis, Taurantha and Urochilus. These changes were not adopted widely by Australian herbaria as the data appeared to support a monophyletic group. In 2010, further molecular work reinstated Pterostylis as a monophyletic group with two subgenera distinguishing species with lateral sepals that are bent sharply downwards from those with the lateral sepals bent backwards.
The genus name is derived from the Greek words pteron meaning 'wing' and stylos meaning 'pillar' or 'post', but in orchids, generally applies to the column.
The closest relative of Pterostylis is Achlydosa, restricted to New Caledonia and the sole other genus of subtribe Pterostylidinae.
Distribution and habitat
Orchids in the genus Pterostylis occur mostly in Australia but are also found in New Zealand, including some of its smaller islands such as Chatham Island, and in New Caledonia, New Guinea, New Britain, New Ireland and on Seram Island in Indonesia. In Australia they are found in all states and Lord Howe Island, but not in the Northern Territory. They grow in a wide range of habitats, especially in temperate zones and are found in grassland, heath, scrub, woodland and forest, including rainforest. They sometimes grow in semi-arid areas but usually near rocks or crevices where there is run-off during rain. In tropical regions they tend to grow at higher altitudes where temperatures are lower. Most have periods of dormancy which coincide with climatic extremes, surviving as small tubers until favourable conditions return.Ecology
Most greenhoods are pollinated by insects, nearly always by tiny flies from the family Mycetophilidae or by mosquitoes. The insect approaches the flower from downwind, as if attracted by a scent and usually lands on the galea. The insect then enters the flower and either because it has passed a balance point, or because it has touched a sensitive part of the labellum, the labellum moves forward trapping the insect between the column wings, the labellum and other flower parts. Observation of the insect's reaction to entrapment is difficult to observe, but in its struggle to escape, it either deposits pollinia from a previously visited flower or contacts the sticky viscidium and pollinia are attached, then carried to another flower. The features of an actively-moving labellum, along with the galea, are unique to these orchids.Uses
Use in horticulture
Greenhoods are easily grown in pots and usually flower well, filling the pot in a few years. Pterostylis curta and P. nutans can be grown in commercial orchid potting mix with coarse gravel added. A bushhouse or cool glasshouse are needed for some species. Greenhoods need regular watering in the growing seaseon but must be kept dry when dormant.Species
The following is a list of species of Pterostylis accepted by Plants of the World Online as at January 2023, apart from Pterostylis striata, a name that is accepted by the Australian Plant Census:Pterostylis abrupta D.L.Jones – tablelands greenhoodPterostylis aciculiformis M.A.Clem. & D.L.Jones – needle-point rustyhood, slender ruddyhoodPterostylis actites D.L.Jones & C.J.French - coastal short-eared snail orchidPterostylis acuminata R.Br. – sharp greenhood, pointed greenhoodPterostylis × aenigma D.L.Jones & M.A.Clem. – enigmatic greenhoodPterostylis aestiva D.L.Jones – long-tongued summer greenhoodPterostylis agathicola D.L.Jones, Molloy & M.A.Clem. – kauri greenhood Pterostylis agrestis G.N.Backh.Pterostylis alata Rchb.f. – striped greenhoodPterostylis allantoidea R.S.Rogers – shy greenhoodPterostylis alobula L.B.Moore - winter greenhood Pterostylis alpina R.S.Rogers – mountain greenhoodPterostylis alveata Garnet – coastal greenhoodPterostylis amabilis D.L.Jones Pterostylis ampliata D.L.Jones – large autumn greenhoodPterostylis anaclasta Janes & DurettoPterostylis anatona D.L.Jones – Eungella greenhoodPterostylis aneba D.L.JonesPterostylis angulata D.L.Jones & C.J.French – Helena River snail orchid, limestone snail orchidPterostylis angusta A.S.George – narrow-hooded shell orchid, narrow shell orchidPterostylis antennifera D.L.JonesPterostylis aphylla Lindl. – leafless greenhoodPterostylis aquilonia D.L.Jones & B.Gray – northern cobra greenhoodPterostylis arbuscula D.L.Jones & C.J.French – dark banded greenhoodPterostylis arenicola M.A.Clem. & J.Stewart – sandhill rustyhoodPterostylis areolata Petrie Pterostylis aspera D.L.Jones & M.A.Clem. – rough shell orchidPterostylis atrans D.L.Jones – dark-tip greenhood, blunt-tongue greenhoodPterostylis atriola D.L.Jones – Snug greenhoodPterostylis atrosanguinea D.L.Jones & C.J.FrenchPterostylis auriculata Colenso Pterostylis australis Hook.f. – southern greenhood Pterostylis banksii A.Cunn. Pterostylis baptistii Fitzg. – king greenhoodPterostylis barbata Lindl. – western bearded greenhood, bird orchidPterostylis barringtonensis G.N.Backh. – Barrington leafy greenhoodPterostylis basaltica D.L.Jones & M.A.Clem. – basalt rustyhood, basalt greenhoodPterostylis bicolor M.A.Clem. & D.L.Jones – black-tip greenhoodPterostylis bicornis D.L.Jones & M.A.Clem. – horned greenhoodPterostylis biseta Blackmore & Clemesha – bristled rustyhoodPterostylis boormanii Rupp – sikh's whiskers, baggy britches, or Boorroans green-hoodPterostylis borealis D.L.JonesPterostylis bracteata J.M.H.ShawPterostylis brevichila D.L.Jones & C.J.French – dwarf shell orchidPterostylis brevisepala D.L.Jones & C.J.FrenchPterostylis brinsleyi J.M.H.ShawPterostylis brumalis L.B.Moore – kauri greenhood Pterostylis brunneola D.L.Jones & C.J.French – giant snail orchidPterostylis bryophila D.L.Jones – Hindmarsh Valley greenhoodPterostylis bureaviana Schltr. Pterostylis calceolus M.A.Clem. – Bungonia rustyhoodPterostylis caligna M.T.MathiesonPterostylis cardiostigma D.Cooper Pterostylis caulescens L.O.Williams Pterostylis cernua D.L.Jones, Molloy & M.A.Clem. – Westland greenhood Pterostylis chaetophora M.A.Clem. & D.L.Jones – Taree rustyhood, tall rusthood or ruddy hoodPterostylis cheraphila D.L.Jones & M.A.Clem. – floodplain rustyhoodPterostylis chlorogramma D.L.Jones & M.A.Clem. – green-striped leafy greenhoodPterostylis chocolatina G.N.Backh. – chocolate-lip leafy greenhoodPterostylis ciliata M.A.Clem. & D.L.Jones – hairy rufous greenhood, tall rusthood or hairy rustyhoodPterostylis clavigera Fitzg. – hairy snail orchidPterostylis clivicola G.N.Backh.Pterostylis clivosa D.L.JonesPterostylis cobarensis M.A.Clem. – inland rustyhood, Cobar rustyhoodPterostylis coccina Fitzg. – scarlet greenhoodPterostylis collina M.A.Clem. & D.L.Jones – shiny bull orchidPterostylis commutata D.L.Jones – midland rustyhoodPterostylis concava D.L.Jones & M.A.Clem. – pouched greenhood, cupped banded greenhoodPterostylis concinna R.Br. – trim greenhoodPterostylis conferta G.N.Backh. – leprechaun greenhood, basalt midget greenhood- * Pterostylis conferta G.N.Backh. subsp. conferta
- * Pterostylis conferta subsp. occidentalis J.M.H.Shaw Pterostylis × conoglossa UptonPterostylis corpulenta D.L.JonesPterostylis crassa G.N.Backh. – coarse leafy greenhoodPterostylis crassicaulis G.N.Backh. – alpine swan greenhoodPterostylis crassichila D.L.Jones – plump northern greenhoodPterostylis crebra D.L.JonesPterostylis crebriflora D.L.Jones & C.J.FrenchPterostylis crispula D.L.Jones & C.J.FrenchPterostylis cucullata R.Br. – leafy greenhoodPterostylis curta R.Br. – blunt greenhoodPterostylis cycnocephala Fitzg. – swan greenhoodPterostylis daintreana F.Muell. ex Benth. – Daintree's greenhoodPterostylis decurva R.S.Rogers – summer greenhoodPterostylis depauperata F.M.Bailey – keeled greenhoodPterostylis despectans M.A.Clem. & D.L.Jones – lowly rustyhoodPterostylis dilatata A.S.George – robust snail orchidPterostylis diminuta G.N.Backh. – small-flowered leafy greenhoodPterostylis divaricata L.M.Copel. & D.L.JonesPterostylis diversiflora J.M.H.ShawPterostylis dolichochila D.L.Jones & M.A.Clem. – long-tongued shell orchidPterostylis dubia R.Br. – blue-tongued greenhoodPterostylis echinulata D.L.Jones & C.J.French – hairy-leafed snail orchidPterostylis ectypha D.L.Jones & C.J.FrenchPterostylis elegans D.L.Jones – elegant greenhoodPterostylis elegantissima D.L.Jones – elegant rufous greenhoodPterostylis erecta T.E.Hunt - upright maroonhoodPterostylis eremaea D.L.Jones & C.J.FrenchPterostylis erubescens D.L.Jones & C.J.French – red sepaled snail orchid Pterostylis erythroconcha M.A.Clem. & D.L.Jones – red shell orchidPterostylis exalla G.N.Backh.Pterostylis excelsa M.A.Clem. – tall rustyhood, dry land green-hoodPterostylis exquisita D.L.JonesPterostylis exserta D.L.Jones – exserted rufous greenhoodPterostylis extensa D.L.JonesPterostylis extranea Janes & DurettoPterostylis faceta D.L.Jones & C.J.FrenchPterostylis falcata R.S.Rogers – sickle greenhoodPterostylis ferruginea G.N.Backh. – Bangham rustyhoodPterostylis fischii Nicholls – Fisch's greenhoodPterostylis flavovirens R.J.Bates – coastal banded greenhoodPterostylis foliacea D.L.JonesPterostylis foliata Hook.f. – slender greenhoodPterostylis frenchii A.P.Br. – tuart rufous greenhoodPterostylis fuliginosa D.L.Jones & C.J.French Pterostylis furcata Lindl. – forked greenhoodPterostylis × furcillata RuppPterostylis furva D.L.JonesPterostylis galgula D.L.Jones & C.J.FrenchPterostylis gibbosa R.Br. – Illawarra rustyhood, Illawarra greenhoodPterostylis glebosa D.L.Jones & C.J.French – clubbed snail orchidPterostylis glyphida G.N.Backh.Pterostylis gracilis NichollsPterostylis gracillima D.L.Jones & C.J.FrenchPterostylis graminea Hook.f. – grass-leaved greenhood Pterostylis grandiflora R.Br. – superb greenhood, cobra greenhoodPterostylis grossa D.L.JonesPterostylis hadra D.L.JonesPterostylis hamata Blackmore & Clemesha – southern hooked rustyhoodPterostylis hamiltonii Nicholls – red-veined shell orchidPterostylis heberlei D.L.Jones & C.J.FrenchPterostylis hians D.L.Jones – opera house orchidPterostylis hildae Nicholls – rainforest greenhoodPterostylis hispidula Fitzg. – small nodding greenhood, box greenhoodPterostylis humilis R.S.Rogers Pterostylis incognita G.N.Backh. – Sale greenhoodPterostylis × ingens D.L.JonesPterostylis insectifera M.A.Clem. – insect-lipped rufous greenhood, leaden rustyhoodPterostylis irsoniana Hatch Pterostylis irwinii D.L.Jones Pterostylis jacksonii D.L.Jones & C.J.French – southwest granite snail orchidPterostylis jeanesii Reiter, Kosky & M.A.Clem.Pterostylis jonesii G.N.Backh. – montane leafy greenhoodPterostylis karri D.L.Jones & C.J.French – karri snail orchidPterostylis laxa Blackmore – antelope greenhoodPterostylis lepida G.N.Backh. – Halbury greenhoodPterostylis leptochila M.A.Clem. & D.L.Jones – Ravensthorpe rufous greenhood, narrow-lipped rustyhoodPterostylis limbatus J.M.H.ShawPterostylis lineata G.N.Backh. – Blue Mountains leafy greenhoodPterostylis lingua M.A.Clem. – large-lipped rustyhoodPterostylis littoralis R.J.Bates – coastal leafy greenhoodPterostylis loganii G.N.Backh. – Logan's leafy greenhoodPterostylis longicornis D.L.Jones & C.J.FrenchPterostylis longicurva Rupp – long-tongued greenhoodPterostylis longifolia R.Br. – common leafy greenhood, tall greenhoodPterostylis longipetala Rupp – curved greenhoodPterostylis lortensis D.L.Jones & C.J.French – Lort River snail orchidPterostylis lustra D.L.Jones – small sickle greenhoodPterostylis macilenta G.N.Backh.Pterostylis macrocalymma M.A.Clem. & D.L.Jones – large-hooded rufous greenhood, Murchison rustyhoodPterostylis macrosceles D.L.Jones – slender rufous greenhoodPterostylis macrosepala G.N.Backh.Pterostylis major G.N.Backh.Pterostylis maxima M.A.Clem. & D.L.Jones – large rustyhoodPterostylis melagramma D.L.Jones – black-stripe leafy greenhoodPterostylis meridionalis D.L.Jones & C.J.FrenchPterostylis metcalfei D.L.Jones – Metcalfe's greenhood, large kinked greenhood or Ebor greenhoodPterostylis microglossa D.L.Jones & C.J.French – Kalbarri shell orchidPterostylis micromega Hook.f. – swamp greenhood Pterostylis microphylla D.L.Jones & C.J.French – small rosette snail orchidPterostylis mirabilis R.J.Bates – nodding rufous-hoodPterostylis mitchellii Lindl. – Mitchell's rustyhoodPterostylis montana Hatch Pterostylis monticola D.L.Jones – large mountain greenhoodPterostylis multiflora G.N.Backh. – tall tiny greenhoodPterostylis multisignata D.L.JonesPterostylis mutica R.Br. – midget greenhoodPterostylis mystacina Janes & DurettoPterostylis nana R.Br. – dwarf snail orchidPterostylis nichollsiana D.L.JonesPterostylis nigricans D.L.Jones & M.A.Clem. – dark greenhoodPterostylis nutans R.Br. – nodding greenhood, parrot's beak orchidPterostylis oblonga D.L.Jones – coastal maroonhoodPterostylis obtusa R.Br. – blunt greenhoodPterostylis oliveri Petrie Pterostylis ophioglossa R.Br. – snake-tongue greenhoodPterostylis orbiculata D.L.Jones & C.J.French coastal banded greenhoodPterostylis oreophila Clemesha – Kiandra greenhood, blue-tongued greenhoodPterostylis ovata M.A.Clem. – Gawler Range rustyhoodPterostylis paludosa D.L.Jones, Molloy & M.A.Clem. – swamp greenhoodPterostylis papuana RolfePterostylis parca G.N.Backh. – Lithgow leafy greenhoodPterostylis parva D.L.Jones & C.J.French – fawn snail orchidPterostylis parviflora R.Br. - tiny greenhoodPterostylis patens Colenso Pterostylis peakalliana Reiter, Kosky & M.A.Clem.Pterostylis pearsonii Janes & DurettoPterostylis pedina Janes & DurettoPterostylis pedoglossa Fitzg. – prawn greenhoodPterostylis pedunculata R.Br. – upright maroonhoodPterostylis perculta D.L.Jones – ruddy hoodPterostylis petiolata D.L.JonesPterostylis petrosa D.L.Jones & M.A.Clem. – Riverina rustyhoodPterostylis picta M.A.Clem. – painted rufous greenhood, painted rustyhoodPterostylis planulata D.L.Jones & M.A.Clem. – flat rustyhoodPterostylis platypetala D.L.Jones & C.J.French – broad petaled snail orchidPterostylis plumosa Cady - bearded greenhood, plumed greenhoodPterostylis porrecta D.L.Jones, Molloy & M.A.Clem. Pterostylis praetermissa M.A.Clem. & D.L.Jones – Mount Kaputar rustyhoodPterostylis prasina G.N.Backh. – mallee leafy greenhoodPterostylis pratensis D.L.Jones – Liawenee greenhoodPterostylis precatoria D.L.Jones & C.J.FrenchPterostylis procera D.L.Jones & M.A.Clem. – short-lipped greenhoodPterostylis psammophila R.J.Bates – two-bristle greenhoodPterostylis puberula Hook.f. – dwarf greenhood, snail greenhood Pterostylis pulchella Messmer – waterfall greenhood, escarpment greenhood or pretty greenhoodPterostylis pusilla R.S.Rogers – tiny rustyhoodPterostylis pyramidalis Lindl. - tall snail orchid, leafy snail orchidPterostylis × ralphcranei D.L.Jones & M.A.Clem.Pterostylis readii D.L.JonePterostylis recurva Benth. – jug orchid, recurved shell orchid, antelope orchid or bull orchidPterostylis reflexa R.Br. – dainty greenhoodPterostylis repanda J.M.H.ShawPterostylis revoluta R.Br. – autumn greenhoodPterostylis riparia D.L.Jones – streamside greenhoodPterostylis robusta R.S.Rogers – sharp-leaf greenhoodPterostylis roensis M.A.Clem. & D.L.Jones – painted rufous greenhood, dark rustyhoodPterostylis rogersii E.Coleman – curled-tongue shell orchidPterostylis rubenachii D.L.Jones – Arthur River greenhoodPterostylis rubescens G.N.Backh. – blushing tiny greenhoodPterostylis rubiginosa L.M.Copel. & D.L.JonesPterostylis rufa R.Br. - red rustyhoodPterostylis russellii T.E.Hunt – Russell's greenhoodPterostylis sanguinea D.L.Jones & M.A.Clem. – red-banded greenhood, dark-banded greenhoodPterostylis sargentii C.R.P.Andrews – frog greenhoodPterostylis saxicola D.L.Jones & M.A.Clem. – Sydney plains rustyhood, Sydney plains greenhoodPterostylis saxosa D.L.Jones & C.J.FrenchPterostylis saxum D.L.Jones & C.J.FrenchPterostylis scabra Lindl. – green-veined shell orchidPterostylis scabrella D.L.Jones & C.J.FrenchPterostylis scabrida Lindl. – rough greenhoodPterostylis scapula D.L.JonesPterostylis scitula D.L.Jones & C.J.French – elegant snail orchidPterostylis scoliosa D.L.Jones – small kinked greenhoodPterostylis setifera M.A.Clem. – bristly rustyhood, sikh's whiskers,Pterostylis silvicultrix D.L.Jones & M.A.Clem. – Chatham Island greenhood, tutukiwi Pterostylis sigmoidea D.L.Jones & C.J.FrenchPterostylis silvicultrix D.L.Jones & M.A.Clem.Pterostylis simulans R.J.BatesPterostylis sinuata Janes & Duretto – Northampton midget greenhood, western swan greenhoodPterostylis smaragdyna D.L.Jones & M.A.Clem. – emerald-lip leafy greenhoodPterostylis spatalium J.M.H.ShawPterostylis spathulata M.A.Clem. – spoon-lipped rufous greenhood, Moora rustyhoodPterostylis spissa G.N.Backh. – cygnet greenhoodPterostylis splendens D.L.Jones & M.A.Clem. Pterostylis squamata R.Br. – southern rustyhood, ruddyhoodPterostylis stenochila D.L.Jones – narrow-lip leafy greenhoodPterostylis stenosepala G.N.Backh. – narrow-sepalled leafy greenhoodPterostylis striata Fitzg. – mainland striped greenhoodPterostylis stricta Clemesha & B.Gray – northern greenhoodPterostylis subtilis D.L.Jones – thin mountain greenhoodPterostylis tanypoda D.L.Jones, Molloy & M.A.Clem. – swan greenhood Pterostylis tasmanica D.L.Jones – small bearded greenhoodPterostylis taurus M.A.Clem. & D.L.Jones – little bull orchidPterostylis telmata D.L.Jones & C.J.FrenchPterostylis tenuicauda Kraenzl. Pterostylis tenuis G.N.Backh. – smooth leafy greenhoodPterostylis tenuissima Nicholls – swamp greenhood
- ''Pterostylis terminalis''