Plants of
South Australia
Pterostylis tenuissima
Orchidaceae
Swamp Greenhood
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Regional Species Conservation Assessments per IBRA subregion.
Least concern
Near threatened
Rare
Vulnerable
Endangered
Critically endangered
Extinct
Data deficient
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Botanical art

Kath Alcock paintings: 4.

Etymology

Pterostylis from the Greek ‘pteron’ meaning a wing and ‘stylis’ meaning a style or column, referring to the prominent wings found at the top of the column in all species. Tenuissima from the Latin 'tenuis' meaning very slender, alluding to this species being the slenderest of all green-hoods.

Distribution and status

Found in the coastal plains of the lower South-east in South Australia, growing in Leptospermum lanigerum scrub on alkaline soils in swamps and along the edges of rivers and creeks, often forming dense colonies. Also found in Victoria. Native. Rare in South Australia. Rare in Victoria. Vulnerable in Australia under the EPBC Act.
Herbarium region: South Eastern
NRM region: South East
AVH map: SA distribution map (external link)

Plant description

Annual terrestrial orchid growing from an underground tuber to 30 cm tall with a single nodding flower and forming a basal rosette of 3-8 dark green, glossy ovate leaves. The basal leaves are only present when non-flowering. The flowering form has stem-sheathing leaves to 20 mm long. The single flower have a translucent, green and white striped hood to 20 mm long, labellum narrow, curved, projecting well beyond sinus. Flowering occurs throughout the year but mainly between October and February. Fruits are brown papery ellipsoid capsule. Seeds are very small brown ellipsoid seed with a long translucent brown mesh-like covering.

Seed collection and propagation

Collect seeds between December and March. Collect fat capsules as they start to dry and turn brown. Pods will split and release the seeds quickly and will require monitoring. To increase the chances of collecting mature pods, it is recommended that a small breathable bag (ie. Organza bags) be used to enclose the developing capsules. Place the capsules in a container that will hold fine seeds and leave to dry for a few weeks or until the capsule split. Then carefully hold the capsule and tap it gently to release the seeds. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place, refrigerator or in liquid nitrogen. For the NVC South East Orchid Project one population consisting of more than 15 individuals was recorded from Pick Swamp. Approximately 16,000 seeds (0.007 g) were banked from this population. Seed viability of this collection was 65%. Seed germination in Pterostylis species is difficult in the absence of symbiotic mycorrhizal fungi.

Seeds stored:
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LocationNo. of seeds
(weight grams)
Number
of plants
Date
collected
Collection number
Collection location
Date
stored
% ViabilityStorage
temperature
BGA20,000 (0.007 g)523-Jan-2014C. Dickson
South Eastern
1-Nov-201665%-80°C
Location: BGA — the seeds are stored at the Adelaide Botanic Gardens, MSB — the seeds are stored at the Millennium Seed Bank, Kew, England.
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.