Swamp Greenhood - Image: Andrew Pritchard
| Swamp Greenhood Pterostylis tenuissima | ||||||||||||
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The Swamp Greenhood Pterostylis tenuissima has a single translucent white flower up to 20mm long, with dark green stripes and toning. Flower stems are green, grow to approximately 30cm tall and have up to six small stem sheathing leaves.
All known records of Swamp Greenhood in Victoria. Source: Victorian Biodiversity Atlas 2018
The Swamp Greenhood orchid is thought to be exclusively associated with Swamp Scrub vegetation, a dark, dense, wet habitat comprising predominantly Woolly Tea-tree and to a lesser extent Scented Paperbark that occurs in wet conditions with black alluvial soil such as soaks, swamps and along watercourses.
Typical Swamp Scrub habitat near Curdie Vale dominated by Woolly Tea-tree.
Swamp Greenhood grows in the open understorey beneath this dense canopy along with a huge diversity of grasses, sedges, herbs, moss and fungi. It is sometimes found on or beside animal tracks through the Swamp Scrub. Orchids are rarely found in the closed areas of understorey dominated by dense Gahnia (Saw Sedge).
Flowering occurs throughout the year and is more prolific during summer months. Most of the population occurs in South West Victoria with only one other site at Wilsons Promontory.
Swamp Greenhood in flower.
Swamp Greenhood seed capsule forming.
Swamp Greenhood seed dispersed from the seed capsule.
The remaining populations of Swamp Greenhood are closely dependent on the retention of Swamp Scrub vegetation, particularly in the Curdie Vale, Peterborough, Nelson and Tyrendarra areas.
Whilst some Swamp Scrub habitat is in parks and reserves there are significant areas in private ownership which require careful management. The main threats are related to the quality of the Swamp Scrub habitat. Clearing results in complete loss of habitat, over grazing tends to thin out vegetation allowing more light to enter, which alters microclimate conditions. Physical impacts from overgrazing include trampling of orchids, compaction and pugging of soil. Introduced weeds smother out the Swamp Greenhood and compete for germination space. Over grazing by rabbits and wallabies can reduce seed production.
The majority of Swamp Greenhooods grow on privately owned land. Farmers and other landholders play a major role in protecting this species. Many landholders have protected the Swamp Scrub habitat on their properties by limiting or excluding stock access and controlling weeds.
The highest priority is to focus on protection of habitat quality both on private property and within parks and reserves. This involves negotiating cooperative management agreements with private landholders and ensuring populations in parks and reserves are recognised and protected. At present there are twelve priority sites in Victoria (11 of these in the south-west and one site at Wilson’s Promontory).
Private landholders have played an important role in some areas where they have generously assist with research and monitoring by allowing surveys to be conducted on their land. Other actions include conducting surveys to locate suitable habitat areas and any additional populations, routine population monitoring at known sites and assessment of threats. A sample of seed from known sites is collected and stored to safeguard against catastrophic loss of a population.
See also: Royal Botanic Gardens - Orchid Conservation Program