Trisetum is a genus of grasses in the family Poaceae (order Poales), commonly known as oatgrass. The genus is distributed across temperate, subarctic, and alpine habitats throughout much of the world, occurring in Europe, the Americas, Asia, and on oceanic islands such as the Hawaiian Islands and Juan Fernández Islands.
Trisetum grasses are typically slender, tufted perennials characteristic of open meadows, mountain pastures, and rocky slopes at higher elevations. The genus name is associated with the three-awned or three-bristled structure of the florets, a morphological trait that distinguishes it within the broader grass family.
Historically, Trisetum encompassed more than 70 species, but taxonomic revision over the past decade has substantially reduced its circumscription. Several groups have been separated into their own genera, including Graciliotrisetum and Sibirotrisetum, and other species have been transferred elsewhere. Plants of the World Online currently recognizes eight accepted species. Among the better-known representatives are Trisetum flavescens (golden oatgrass), native to Europe, the Azores, northwestern Africa, and western Asia; Trisetum glomeratum, endemic to the Hawaiian Islands; and Trisetum caudulatum, found in the Juan Fernández Islands, Chile, and southern Argentina.
Distribution
Trisetum occurs across temperate, subarctic, and alpine regions worldwide, with species recorded in Europe (including the Apennines), the Azores, northwestern Africa, western and central Asia, the Himalayas, China, central Peru, Chile, Argentina, and the Hawaiian Islands.
Taxonomy Notes
Trisetum formerly comprised over 70 species, but recent taxonomic work has substantially narrowed the genus. Several segregate genera have been recognized, including Graciliotrisetum and Sibirotrisetum, and additional species have been moved to other genera. Plants of the World Online currently accepts eight species.
