Rytidosperma unarede

It is an slender perennial tufted grass, growing to about 45 cm in height. The leaf blade grows up to 40 in length and 3.5 mm wide, or is tightly inrolled. The panicle is erect, slightly branched, 5–10 cm long and 1–2.3 cm wide. R. unarede has 2n = 48 chromosomes.

Identification. As a Rytidosperma, the easiest way to identify R. unarede is to select a single floret (which will contain a single awn, two lateral lobes, and usually three rows of hairs - one on the callus and two on the lemma). The arrangement of the hairs, as well as the relative lengths of the awn, lateral lobes, sometimes the callus can help identify to species, using a key such as that found in the New Zealand Flora.

Similar species. R. unarede is most similar to R. biannulare. These two species are differentiated from all other New Zealand Rytidosperma by their long lateral lemma lobes and upper lemma hairs, which exceed the awn column, and by their short lower lemma hairs. However, they are differentiated from one another by R. biannulare having an awn column that is much longer than the palea.

The grass is native to New Zealand, where it is found on the Kermadec, Three Kings, North, South, Stewart, and Chatham Islands. It is apparently rare to west of Main Divide in the South Island. R. unarede was first discovered on the Kermadec Islands in 1994 by botanist A. E. Wright. It is possible that it is a new arrival which is still localised, given that it is currently found only in one place on the islands. It is also a rare inhabitant of Australia's subtropical Lord Howe Island in the Tasman Sea.

Type specimen. The type specimen of R. unarede was collected near the Akaroa Peninsula by Étienne Raoul in 1843.

The rust fungus Uromyces danthoniae, a species found that grows parasitically on the leaves of several Rytidosperma species in New Zealand and Australia, infects Rytidosperma unarede. It forms dense clusters of orange-brown aecidia on both surfaces of the leaf. It is also a host of Sphaerodothella danthoniae, a sac fungus that produces black, shiny leaf spots that occasionally coalesce into straight to irregular lines in the leaf surface of several species of Rytidosperma.

Rytidosperma: 'wrinkled seed' from the Greek 'rhytidos' = wrinkled and 'sperma' = seed unarede: derived from the Te Reo Māori name for the grass - according to Raoul, 'Vulgo Unarede' or, the common name is unarede.