Swamp mignonette orchid | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Monocots |
Order: | Asparagales |
Family: | Orchidaceae |
Subfamily: | Orchidoideae |
Tribe: | Diurideae |
Genus: | Microtis |
Species: | M. atrata
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Binomial name | |
Microtis atrata | |
Synonyms [1] | |
Microtis atrata, commonly known as the swamp mignonette orchid [2] or yellow onion orchid [3] and sometimes as Microtidium atratum, [4] is a species of orchid endemic to southern Australia. It has a single thin leaf and up to forty or more yellowish-green flowers. The flowers are the smallest of any Australian ground-dwelling orchid. The orchid usually grows in large colonies after fire and although small, are easily seen because of their very large numbers in their blackened surroundings.
Microtis atrata is a terrestrial, perennial, deciduous, herb with an underground tuber and a single erect, smooth, more or less solid leaf, 30–90 mm (1–4 in) long and about 3 mm (0.1 in) wide. Between two and forty or more yellowish-green flowers are densely crowded along a flowering stem 10–40 mm (0.4–2 in) long, reaching to a height of 50–120 mm (2–5 in). The plants are sometimes up to 200 mm (8 in) tall if growing in water. At about 2 mm (0.08 in) long and wide, the flowers are the smallest of any terrestrial Australian orchid, and as they age, they turn black. The dorsal sepal is egg-shaped to round, about 1 mm (0.04 in) long and wide and forms a hood over the column. The lateral sepals are oblong, less than 1 mm (0.04 in) long and spread apart from each other. The petals are egg-shaped and concave and the labellum is oblong to egg-shaped. Flowering occurs from September to December and is stimulated by fire the previous summer. [2] [3] [4] [5]
Microtis atrata was first formally described in 1840 by John Lindley and the description was published in A Sketch of the Vegetation of the Swan River Colony. [6] [7] The specific epithet (atrata) is a Latin word meaning "dressed in black", [8] referring to the colour of the dried flowers. [9]
Some authorities give this species the name Microtidium atratum [2] [4] but this name is not widely accepted. [1] [3]
The swamp mignonette orchid occurs in the south-west of Western Australia, the south-east of South Australia, in southern Victoria and northern Tasmania. It grows in swampy places and in winter-wet depressions, sometimes in standing water and can form colonies of enormous numbers of plants after summer fire. [5] [9] [10]
Microtis atrata is classified as "not threatened" in Western Australia by the Western Australian Government Department of Parks and Wildlife, [11] but is regarded as "endangered" in South Australia [12] and as "rare" in Tasmania. [4]