Bothriochloa is a widespread genus of grasses in the family Poaceae (order Poales), collectively known as beardgrasses or bluestems. The genus is native to all inhabited continents and many islands, with individual species distributed across the Americas, Eurasia, Africa, Australia, and Pacific island groups. It is one of the more species-rich warm-season grass genera, encompassing roughly 35–40 recognised species.
Members of Bothriochloa are perennial or annual warm-season grasses, characterised by the pitted or grooved surface of their spikelets — the morphological feature that gives the genus its name. The plants typically form clumps or tufts and bear racemose inflorescences. Several species carry awns on their fertile florets, though awnless forms exist (notably B. exaristata, whose epithet means "without awn").
The genus has considerable ecological breadth. Some species, such as B. ischaemum (yellow bluestem) and B. pertusa (pitted beardgrass), have become invasive outside their native ranges, colonising disturbed grasslands and outcompeting native vegetation. Others, such as B. decipiens and B. erianthoides, are valued components of native Australian grassland systems. In the Americas, species like B. alta (tall beardgrass) and B. barbinodis (cane bluestem) are characteristic of open rangelands from the southwestern United States to South America.
Etymology
The name Bothriochloa combines two ancient Greek words: βοθρίον (bothríon), meaning "small pit or trench", and χλόη / χλόα (khlóa), meaning "new green shoot or blade of grass". The name refers to the pitted surface of the spikelets that is characteristic of the genus.
Distribution
Bothriochloa is native to a very broad range spanning all inhabited continents and many islands. Species occur across Eurasia (from the Iberian Peninsula and Canary Islands to Japan and the Malay Archipelago), Africa, Madagascar, the Arabian Peninsula, the Indian subcontinent, Australia, New Guinea, and the Americas from the southwestern United States south to Patagonia. Several species have disjunct or expanded distributions through natural dispersal or human introduction, including records of B. ewartiana at Gooty Fort Hill, Andhra Pradesh, India — far from its primary Australian range.
Ecology
Warm-season grasses of Bothriochloa are adapted to open, often seasonally dry habitats including savannas, grasslands, roadsides, and disturbed ground. Some species are ecologically important components of native grasslands in Australia and the Americas. Others, particularly B. ischaemum (yellow bluestem, native to Eurasia) and B. pertusa (pitted beardgrass, native to tropical Asia), are documented invasives that can suppress native plant communities in areas where they have been introduced.
