forest sun orchid

Thelymitra arenaria is a tuberous, perennial herb with a single leathery, channelled, dark green linear to lance-shaped leaf 150–300 mm (6–10 in) long and 8–18 mm (0.3–0.7 in) wide with a purplish base. Between two and sixteen purplish flowers 16–26 mm (0.6–1 in) wide are borne on a flowering stem 240–400 mm (9–20 in) tall. There are usually and two bracts on the flowering stem. The sepals and petals are 8–15 mm (0.3–0.6 in) long and 4–8 mm (0.2–0.3 in) wide. The column is pale blue with dark blue streaks, 4.5–6 mm (0.18–0.24 in) long and 2.5–3.5 mm (0.098–0.14 in) wide. The lobe on the top of the anther is dark brown with a yellow tip and gently curved. The side lobes curve upwards and have dense, hairbrush-like tufts of white hairs. The flowers are self-pollinating and only open on warm to hot, humid days. Flowering occurs from October to December.

Forest sun orchid is widespread and common within most of its range. It grows in a wide range of habitats from grassland to forest and is found in southern New South Wales, the Australian Capital Territory, in the southern half of Victoria, in south-eastern South Australia and in Tasmania.