Tridens is a genus of perennial grasses in the family Poaceae, placed within the order Poales. The genus comprises approximately 13–14 accepted species, all native to the Americas. Plants in this genus are typically perennial bunchgrasses found across a wide latitudinal range, from Ontario in Canada through the eastern, central, and southwestern United States, into Mexico, and south through South America as far as Argentina and Uruguay.
The genus is perhaps best known in North America for Tridens flavus (purpletop), a widespread warm-season grass of the eastern and central United States distinguished by its purplish panicles. Other members include Tridens ambiguus (pine barren fluffgrass), restricted to the sandy soils of the southeastern coastal plain, and Tridens strictus (longspike tridens), found across the southeastern and south-central United States. Tridens congestus (pink fluffgrass) and Tridens texanus are characteristic of arid to semi-arid habitats in Texas, New Mexico, and northern Mexico.
The genus also extends into South America, with species such as Tridens brasiliensis occurring in Brazil, Paraguay, Uruguay, and Argentina. Tridens × oklahomensis is a naturally occurring hybrid between T. flavus and T. strictus, recorded from Oklahoma.
Distribution
Tridens is distributed across the Americas, with most species occurring in the United States and Mexico. The range extends from Ontario, Canada, through the eastern, central, and southwestern United States, south through Mexico (including Chihuahua, Durango, Coahuila, and Tamaulipas), and into South America, where species are found in Brazil, Paraguay, Uruguay, Argentina, Guyana, Venezuela, and Colombia.
Ecology
Species in the genus occupy diverse habitats across the Americas. Tridens ambiguus is associated with the sandy, acidic soils of the southeastern pine barrens, while Tridens congestus and Tridens texanus are adapted to the drier, often rocky or sandy substrates of the southwestern United States and northern Mexico. Tridens flavus is a common warm-season grass of roadsides, open woodlands, and disturbed ground in the eastern and central United States.
Taxonomy Notes
The genus Tridens is placed in the family Poaceae (grasses). GBIF records 14 accepted descendants. Tridens × oklahomensis is recognized as a natural hybrid between T. flavus and T. strictus. The Wikipedia species list notes several species formerly included in the genus that have since been reassigned.
