Arrhenatherum, commonly known as oat-grass or button-grass, is a small genus of perennial grasses in the family Poaceae (order Poales). Native to Eurasia and North Africa, the genus ranges from Iceland and Portugal in the west to Kazakhstan in the east, extending south through the Mediterranean region into North Africa.
Plants in this genus are robust perennials with yellowish roots and shining stems that can reach up to 1.80 m (about 6 ft) in height, though the above-ground portions die back in winter. The leaves are hairless and bear blunt ligules. The inflorescence takes the form of an open panicle bearing two-flowered bisexual spikelets, giving the plants a resemblance to wild oat (Avena) or fescue (Festuca).
The most widespread and well-known member is Arrhenatherum elatius (false oat-grass or tall oat-grass), which has been widely naturalized beyond its native range — occurring in East Asia, Australia, New Zealand, and the Americas. Other species include A. album (Mediterranean) and A. pallens (Portugal). Several species formerly assigned to Arrhenatherum have been transferred to related genera including Helictochloa, Helictotrichon, and Avenula.
Etymology
The genus name Arrhenatherum derives from the Greek words arrhen (male) and ather (awn or beard), referring to the awned male floret characteristic of the spikelets.
Distribution
Arrhenatherum is native to Eurasia and North Africa, with the range extending from Iceland and the Canary Islands in the west to Kazakhstan in the east, and southward through the Mediterranean basin. A. elatius, the most widespread species, has been widely naturalized in East Asia, Australia, New Zealand, and throughout the Americas.
Ecology
Oat-grasses are very common grassland perennials, frequently found in meadows, roadsides, and disturbed habitats. Wild forms can resemble wild oat (Avena) or fescue (Festuca), with which they often co-occur in Eurasian grassland communities.
