Tarengo Leek Orchid - profile

Indicative distribution

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Key:

known

predicted

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: 06 Nov 2023

Description

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.

Distribution

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.

Threats

Previous threats appear to have been loss, degradation and fragmentation of habitat and populations to residential, infrastructure and agricultural developments.
Inappropriate mowing or grazing regimes, especially in spring and summer when above-ground parts are present.
Threatened by competition from other plant species, both native (e.g. kangaroo grass, tea- trees) and non-native (e.g. sweet vernal-grass Anthoxanthum odoratum).
Particularly vulnerable to chance extinctions because so few populations exist.
Encroachment of herbaceous perennial weeds such as St John's wort and Paterson's curse competing for space and resources.
Current or potential future land management practices do not support conservation.
Road widening and other development pressures at the population at Muswellbrook.

Recovery strategies

A targeted strategy for managing this species has been developed under the Saving Our Species program; click here for details. For more information on the Saving Our Species program click here

Activities to assist this species

Protect known populations from changes to land use.
Do not allow grazing, mowing or other disturbances when above-ground parts are present.
Establish the most effective means of control or management of competing species.
Monitor the known populations to ensure that management is retaining populations.
Mark sites and potential habitat onto maps (of the farm, shire, region, etc) used for planning (e.g. road works, residential and infrastructure developments, remnant protection, rehabilitation).
Search for new populations in potential habitat between the known sites.

Information sources

ACT Government (1997) A leek orchid (Prasophyllum petilum): an endangered species. Action Plan No.4. Environment ACT.
Bishop, T. (2000) Field Guide to the Orchids of New South Wales and Victoria. (New South Wales University Press, Sydney)
Eddy, D. (2002) Managing Native Grassland: a guide to management for conservation, production and landscape protection. (World Wide Fund for Nature Australia, Sydney)
Eddy, D., Mallinson, D., Rehwinkel, R and Sharp. S. (1998) Grassland Flora: a field guide for the Southern Tablelands (NSW & ACT). (Environment ACT, NSW National Parks and Wildlife Service, World Wide Fund for Nature Australia, Australian National Botanic Gardens, Natural Heritage Trust, Canberra)
Harden, G.J. (ed.) (1993) Flora of New South Wales Vol. 4. UNSW Press, Kensington, NSW.
NSW National Parks and Wildlife Service (2003) Draft Recovery Plan for the Tarengo Leek Orchid (Prasophyllum petilum). NSW NPWS, Sydney.

IBRA Bioregion	IBRA Subregion	Known or predicted	Geographic restrictions region

Nandewar	Peel	Known	None
NSW South Western Slopes	Capertee Valley	Predicted	None
NSW South Western Slopes	Inland Slopes	Known	None
Other State	ACT	Known	None
South Eastern Highlands	Capertee Uplands	Known	None
South Eastern Highlands	Kybeyan-Gourock	Known	None
South Eastern Highlands	Monaro	Known	None
South Eastern Highlands	Murrumbateman	Predicted	None
Sydney Basin	Hunter	Known	None
Sydney Basin	Kerrabee	Known	None

Images

Prasophyllum petilum with pollinating Hymenoptera Image 1 of 8.
View slideshow.

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