Prasophyllum triangulare

Description

Prasophyllum triangulare, commonly known as the dark leek orchid, is a species of orchid endemic to the south-west of Western Australia. It is a tall orchid with a single, purplish to blackish, tubular leaf and up to thirty or more relatively large, greyish-purple to brownish-purple flowers. It only flowers after fire the previous summer.Prasophyllum triangulare is a terrestrial, perennial, deciduous, herb with an underground tuber and a single fleshy, purplish to blackish, tube-shaped leaf 250–350 mm (9.8–14 in) long and 2–5 mm (0.08–0.2 in) wide. Between ten and thirty or more flowers are arranged along a flowering spike 90–180 mm (4–7 in) long, reaching to a height of 300–400 mm (10–20 in). The flowers are greyish-purple to brownish-purple, about 12 mm (0.5 in) long and about 9 mm (0.4 in) wide. As with others in the genus, the flowers are inverted so that the labellum is above the column rather than below it. The dorsal sepal is 6–7 mm (0.2–0.3 in) long and about 2 mm (0.08 in) wide and the lateral sepals are a similar size and fused to each other. The petals are 5–6 mm (0.20–0.24 in) long, 2 mm (0.08 in) wide and turn forwards. The labellum is 8–9 mm (0.3–0.4 in) long, about 5 mm (0.2 in) wide and turns sharply upwards near its middle, the upturned part with slightly wavy edges. A broad callus covers most of the labellum, reaching almost to its tip. Flowering occurs in September and October but only following summer fire.