Matthews's Spiral Sun Orchid

Thelymitra matthewsii is a tuberous, perennial herb with a single leaf which is egg-shaped near the base, then suddenly narrows to a linear, curved or spirally twisted upper part. The upper part is 60–90 mm (2–4 in) long and 3–7 mm (0.1–0.3 in) wide. A single (rarely two) dark purple to violet flower with darker veins, 16–20 mm (0.6–0.8 in) wide is borne facing upwards on a flowering stem 100–220 mm (4–9 in) tall. The sepals and petals are 8–10 mm (0.3–0.4 in) long and 4–7 mm (0.2–0.3 in) wide. The dorsal (uppermost) sepal is wider than the other sepals and petals. The column is purplish, 5–6 mm (0.20–0.24 in) long and about 2 mm (0.08 in) wide with two yellow, ear-like arms on the sides. The flowers are self-pollinating, short lived and open on hot, sunny days. Flowering occurs from August to October.

Spiral sun orchid grows in open forest and disturbed sites such as recently exposed soil in gullies. It is found on the extreme north of the North Island of New Zealand, in widely separated sites in Victoria and in south-eastern South Australia. It was previously more widespread in New Zealand then thought to be extinct there until it was rediscovered in the 1980s. It appears to be extinct at the type location.