Flowering stem erect, straight, 15–45(–80) cm tall, 1.5–4.5 mm diam., green to purplish. Leaf linear-lanceolate to lanceolate, attenuate, 10–32 cm long, 5–15 mm wide, fleshy, canaliculate, ribbed abaxially, sheathing at base, dark green grading to purplish towards the base. Inflorescence 2–10(–20)-flowered, loose. Sterile bracts usually 2, sometimes 3. Perianth segments lanceolate to ovate, (9–)15–20(–25) mm long, blue to purplish, occasionally lilac, pink or white. Column slender, 5.5–7 mm long, pink or pale blue; mid-lobe hooding the anther, tubular, highly inflated, dorsally compressed, gently curved through c. 90 deg., pale to dark brown, apex bilobed, yellow, distal margin with 2 prominent forward-pointing horn-like teeth; lateral lobes converging 1–2 mm long, digitiform, porrect at base then curved upwards, each with a toothbrush-like arrangement of white hairs, terminating in front of mid-lobe. Anther inserted about mid-way along column, shortly beaked. Flowers Oct.–Jan.
CVU, NIS, EGU, HSF, HNF, MonT, VAlp. Also NSW, ACT. Grows in alpine and sub-alpine meadows and woodlands often dominated by Snow Gums, or in open montane forests. Substrates are usually sandy or peaty loams.
Flowers open readily on warm days.
Thelymitra alpina could be confused with T. megcalyptra, but the former favours higher altitudes, the column is more elongate, dorsally compressed and the distal margin has two forward-pointing horn-like teeth.
