Diuris palustris

Diuris palustris is a tuberous, perennial herb with a tuft of between eight and ten twisted, linear leaves 100–300 mm (4–10 in) long, 4–6 mm (0.16–0.24 in) wide and folded lengthwise. Up to four flowers 15–20 mm (0.6–0.8 in) wide are borne on a flowering stem 50–150 mm (2–6 in) tall. The flowers are yellow with dark brown spots and blotches. The dorsal sepal is erect, curved backwards near the tip, egg-shaped, 7–10 mm (0.3–0.4 in) long and 5–6 mm (0.20–0.24 in) wide. The lateral sepals are green, 12–15 mm (0.5–0.6 in) long, about 2 mm (0.08 in) wide, turned downwards and parallel to each other. The petals are erect to curved backwards, with an egg-shaped blade 4–6 mm (0.16–0.24 in) long and 3–4 mm (0.1–0.2 in) wide on a dark reddish brown stalk 3–4 mm (0.1–0.2 in) long. The labellum is 7–10 mm (0.3–0.4 in) long and has three lobes. The centre lobe is spatula-shaped, 3–4 mm (0.1–0.2 in) wide and the side lobes are erect, oval, 4–6 mm (0.16–0.24 in) long and 2–3 mm (0.08–0.1 in) wide with rounded teeth near the tip. There are two ridged calli 4–5 mm (0.16–0.20 in) long in the mid-line of the labellum. Flowering occurs from August to October.[2][3][4]

Diuris palustris was first formally described in 1840 by John Lindley and the description was published in his book, The Genera and Species of Orchidaceous Plants.[5][6] The specific epithet (palustris) is a Latin word meaning "marshy" or "boggy".[7]

The swamp doubletail is found in New South Wales, Victoria, Tasmania and South Australia where it is most common. It grows in moist or wet soil in forest, Callitris woodland and grassland.[2][3][4]

Diuris palustris is classed as "vulnerable" under the Victorian Flora and Fauna Guarantee Act 1988 and as "endangered" under the Tasmanian Threatened Species Protection Act 1995.[3][8]