Oryzopsis is a small genus of perennial grasses in the family Poaceae (order Poales), distributed across temperate North America and China. Plants in this genus are commonly known as ricegrass, a name reflecting their resemblance to true rice (Oryza). The genus belongs to the subfamily Pooideae and is characterised by narrow, often wiry leaves and delicate panicles bearing small, one-flowered spikelets with a prominent awn.
The circumscription of Oryzopsis has contracted substantially as molecular phylogenetic studies have clarified relationships within the grass tribe Stipeae. Numerous species once assigned here have been reclassified into related genera including Achnatherum, Piptatherum, Nassella, Stipa, Eriocoma, Ptilagrostis, and several others. In its current, narrower sense, GBIF recognises six accepted species.
The most widespread North American member is Oryzopsis asperifolia (roughleaf ricegrass), which ranges from all ten Canadian provinces and Yukon and Northwest Territories south through the northeastern United States, the Great Lakes region, the Black Hills, and the Rocky Mountains. Other species occupy more restricted western North American ranges in states such as Oregon, Idaho, Wyoming, Colorado, and Montana, while Oryzopsis chinensis is endemic to China and O. holciformis occurs in the eastern Mediterranean region.
Etymology
The genus name Oryzopsis is derived from Oryza (the genus of true rice) and the Greek suffix -opsis ("resembling"), alluding to the superficial similarity between the small grains of these grasses and rice grains.
Distribution
Oryzopsis is native primarily to North America, with species ranging across Canada (all ten provinces, Yukon, and Northwest Territories) and the United States (from the Northeast and Great Lakes south through the Rocky Mountains). The genus also includes one species in China (O. chinensis) and one extending to Israel and the eastern Mediterranean (O. holciformis).
Taxonomy Notes
The genus Oryzopsis has been significantly reduced in scope by modern molecular studies of the grass tribe Stipeae. Species formerly placed here have been redistributed among Achnatherum, Achnella, Anemanthele, Eriocoma, Nassella, Piptatherum, Piptatheropsis, Piptochaetium, Ptilagrostis, Stipa, and Stiporyzopsis. The well-known "Indian ricegrass" (Achnatherum hymenoides, formerly Oryzopsis hymenoides) is one of the more prominent former members. GBIF currently recognises six accepted species in the genus.
