It has a single erect, leathery, channelled, dark green leaf and up to twelve blue flowers with darker veins.

The plant has a bluish green hue and the flowers are self-pollinating, only opening widely on hot days.

Thelymitra peniculata is a glaucous, tuberous, perennial herb with a single erect, dark green, leathery, channelled, linear to lance-shaped leaf 100–300 mm (4–10 in) long and 5–20 mm (0.2–0.8 in) wide with a purplish base.

[2][3][4] Thelymitra planicola was first formally described in 2000 by Jeff Jeanes from a specimen collected near Golden Beach and the description was published in Muelleria .

[3] The glaucous sun orchid grows in grassland and grassy forest in scattered populations in New South Wales and Victoria.