Plants of
South Australia
Microtis atrata
Yellow Onion-orchid
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Regional Species Conservation Assessments per IBRA subregion.
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Data deficient
Coober Pedy
Mount Gambier
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Botanical art

Kath Alcock paintings: 3

Prior names

Microtidium atratum

Microtis minutiflora

Microtis atrata var. viridula


Microtis from the Greek 'mikros' meaning small and 'otos' meaning ear; in reference to the small ear-like column wings. Atrata meaning blackened or dark; referring to the color of dried or senescent plants.

Distribution and status

Found at the bottom of Eyre Peninsula, Kangaroo Island, southern Mount Lofty Ranges and the lower South-east in South Australia. It grows in moist, swampy areas in areas of high rainfall. It is semi-aquatic and is often found adjacent to areas of Leptospermum continentale on the margins of shallow creek lines, soaks and in damp heath. Also found in Western Australia, Victoria and Tasmania. Native. Rare in South Australia. Common in the other states.
Herbarium regions: Eyre Peninsula, Southern Lofty, Kangaroo Island, South Eastern, Green Adelaide
NRM regions: Adelaide and Mount Lofty Ranges, Eyre Peninsula, Kangaroo Island, South East
AVH map: SA distribution map (external link)

Plant description

Grows to 12 cm tall (rarely to 20 cm) with up to 40 flowers. It has a single yellow-green terete leaf often with a dried blackened tip, 3-9 cm long, 3 mm wide. Flowers emerge from just below the leaf apex, they are small, yellow-green, with an eliptical labellum, dorsal sepal to 1 mm. Flowering between September and December. Fruits are brown papery ellipsoid capsule. Seeds are very small brown ellipsoid seed with a long cylindrical translucent brown mesh-like covering.

Seed collection and propagation

Collect seeds between January and February. 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 three populations consisting of more than X individuals in total were recorded from Border Swamp, Bangham Conservation Park and Topperwien Native Forest Reserve. Approximately 60,000 seeds (0.07g) were banked for these three observed populations. Seed viability ranged from 72% to 83%.

Seeds stored:
LocationNo. of seeds
(weight grams)
of plants
Collection number
Collection location
% ViabilityStorage
BGA8,000 (0.009 g)420-Nov-2013KHB815
South Eastern
BGA20,000 (0.028 g)15+3-Nov-2013KHB806
South Eastern
BGA30,000 (0.034 g)70 stems 11-Dec-2013DJD2814
South Eastern
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.