Nature conservation

Threatened species

Tarengo Leek Orchid - profile

Indicative distribution

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The areas shown in pink and/purple are the sub-regions where the species or community is known or predicted to occur. They may not occur thoughout the sub-region but may be restricted to certain areas. ( click here to see geographic restrictions). The information presented in this map is only indicative and may contain errors and omissions.
Scientific name: Prasophyllum petilum
Conservation status in NSW: Endangered
Commonwealth status: Endangered
Profile last updated: 30 Aug 2021


Tarengo Leek Orchid reaches to 35 cm tall. This species can be distinguished from the more common onion orchids (Microtis spp.) that grow in its habitat by the pinkish-purple base to the leaf. Each plant produces a solitary, tubular, fleshy, dull green leaf, growing to 35 cm tall. The flower-stem emerges in mid spring to early summer from a hole near the base of the leaf. The raceme, reaching to 12 cm tall, has about 20 fragrant flowers with pointed tepals. The flowers are usually a pale whitish-green, but can be pink or pale purple. Plants can be very cryptic when growing in small numbers and within tall grasses.

The flowering time for this species varies from north to south. Populations around Muswellbrook and Ilford tend to flower in September, with the Boorowa and Hall populations flowering in October and the Queanbeyan area and Delegate populations in December. Annual abundance varies significantly depending on winter and early spring rainfall, biomass and potentially other variables including the severity of winter frosts.

The NSW Herbarium considers Prasophyllum petilum and Prasophyllum sp. Wybong (C. Phelps ORG5269) to be synonyms (i.e. the same species). This taxonomic recognition will be released in the next Orchidaceae taxonomic update via the Australian Plant Census, which provides a list of currently accepted names. As it stands, the two species are treated as one for NSW regulatory purposes, with the distinction maintained under Commonwealth legislation.


Natural populations are known from a total of five sites in NSW. These are near Boorowa, Queanbeyan area, Ilford, Delegate and a newly recognised population c.10 km west of Muswellbrook. It also occurs at Hall in the Australian Capital Territory. This species has also been recorded at Bowning Cemetery where it was experimentally introduced, though it is not known whether this population has persisted.

Habitat and ecology

  • Grows in open sites within Natural Temperate Grassland at the Boorowa and Delegate sites.
  • Also grows in grassy woodland in association with River Tussock Poa labillardieri, Black Gum Eucalyptus aggregata and tea-trees Leptospermum spp. near Queanbeyan and within the grassy groundlayer dominated by Kanagroo Grass under Box-Gum Woodland at Ilford (and Hall, ACT).
  • Apparently highly susceptible to grazing, being retained only at little-grazed travelling stock reserves (Boorowa & Delegate) and in cemeteries (near Queanbeyan, Ilford and Hall).
  • Flowers in October at Boorowa and Ilford, and December at sites near Queanbeyan and Delegate.
  • Population density at the Boorowa site is higher in the open grassland dominated by wallaby grasses Austrodanthonia spp., compared to that within the denser stands of Kangaroo Grass Themeda australis.
  • Highly colonial, with very large numbers present and very conspicuous at the Boorowa site, but cryptic at the Queanbeyan, Ilford and Delegate sites where low numbers are recorded. The population near Muswellbrook is also small.
  • Flowers are followed by fleshy seed capsules in summer.
  • Plants retreat into subterranean tubers after fruiting, so are not visible above-ground outside of growing periods.

Regional distribution and habitat

Click on a region below to view detailed distribution, habitat and vegetation information.


Recovery strategies

Activities to assist this species

Information sources

IBRA Bioregion IBRA Subregion Known or predicted Geographic restrictions region
NandewarPeel Known None
NSW South Western SlopesCapertee Valley Predicted None
NSW South Western SlopesInland Slopes Known East of Binalong, south and east of Boorowa
Other StateACT Known None
South Eastern HighlandsCapertee Uplands Known None
South Eastern HighlandsKybeyan-Gourock Known None
South Eastern HighlandsMonaro Known None
South Eastern HighlandsMurrumbateman Predicted None
Sydney BasinHunter Known None
Sydney BasinKerrabee Known None