Cormous geophyte up to 30cm. Leaves cylindrical and without prominent veins, up to 15cm long, sometimes withering at flowering time. Sturdy stem bears 7-14 deep blue to purple, rarely white, flowers in a spirally arranged spike; bracts are hard and brown.

Greek: thereios = of or belonging to summer, anthos = bloom of a flower; referring to the summer flowering time of this genus.