Cormous geophyte up to 40cm. Leaves round to oval in cross-section, slender, rush-like, often overtopping flowering stems. Flowers in lax spike, blue to mauve, sometimes white in the throat; perianth tube slender, tepals sub-equal; bracts 3-5mm long.

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

Latin: iuncus = a rush, folium = a leaf; referring to the rush-like leaves of this species.