Apodasmia Genus

Apodasmia is a small genus of rush-like perennial herbs in the family Restionaceae (order Poales), formally described as a genus in 1998 by Briggs and Johnson. The genus comprises around three to five species with a striking disjunct distribution spanning New Zealand, Australia (South Australia, Tasmania, Victoria), and southern Chile — a classic austral pattern reflecting ancient Gondwanan connections.

Plants are dioecious and strongly resemble true rushes, with densely packed, simple, terete culms that are glaucous grey-green, yellow-green, or reddish, and can reach up to roughly 2.6 metres in height. True leaves are absent; instead, photosynthesis occurs in the unbranched culms, while the leaves are reduced to bract-like, dark brown or maroon-black sheathing structures arranged at regular intervals along the stem. Rhizomes are stout (3–7 mm diameter) and covered in closely sheathing, imbricate dark brown scales. This highly reduced leaf morphology is characteristic of the family Restionaceae, an ancient family of wind-pollinated plants well represented in the Southern Hemisphere.

Inflorescences are terminal: males are paniculate or fascicled with numerous stalked spikelets; females are fascicled with mostly sessile spikelets. The three styles are characteristically bright red to orange-red. Fruit are small (c. 1 × 0.5 mm), triquetrous, and indehiscent, with golden-brown reticulate seeds.

The best-known species, Apodasmia similis (Edgar) B.G.Briggs & L.A.S.Johnson — commonly called oioi or jointed wire rush — is endemic to New Zealand, occurring on Three Kings, North, South, Stewart and Chatham Islands. It grows primarily in coastal habitats including estuaries, saltmarshes, and sandy flats, but also occurs inland along lake margins and bordering peat bogs. It carries a conservation status of Not Threatened under the 2023 New Zealand Threat Classification System.