Kath's sun orchid

Thelymitra alcockiae is a tuberous, perennial herb with a single fleshy, channelled, linear to lance-shaped leaf 80–300 mm (3–10 in) long, 5–10 mm (0.2–0.4 in) wide. Between two and twelve pale blue to deep purplish blue, rarely white flowers 15–30 mm (0.6–1 in) wide are arranged on a flowering stem 100–600 mm (4–20 in) tall. The sepals and petals are 10–16 mm (0.4–0.6 in) long, 4–8 mm (0.2–0.3 in) wide and mauve or reddish on the reverse side. The column is pale blue or pinkish, 4–6.5 mm (0.16–0.26 in) long and about 2 mm (0.08 in) wide. The lobe on the top of the anther is brown with a yellow tip, tubular and sharply curved with an inflated tip. The side lobes have dense, mop-like tufts of white hairs. Flowering occurs from August to October.

Kath's sun orchid usually grows in drier habitats including shrubland, open forest and woodland. It is locally common in the north-west of Victoria and in South Australia.