Purple Grama
Bouteloua radicosa
Family: Poaceae
Clustered perennials with dense, hard, knotty base, and rhizomes growing almost 3’ tall. Warm-season grass that is winter dormant.
This species is a part of a group of Boutelouas very similar in appearance being perennials, often caespitose, with short, deciduous inflorescence branches (sometimes appearing as clusters of spikelets) on both sides of the axis which completely fall off, leaving a small nodule behind. B. radicosa is distinguished from B. repens, B. chondrosoides and B. eludens by its hard, knotty, rhizomotous bases. None of these other species have this character. B. radicosa may hybridize with Bouteloua repens and Bouteloua williamsii, which could contribute to its apparent diversity.
There are rare patches of grasslands in Arizona, New Mexico, Chihuahua, and Sonora where this grass is dominant, especially in the Animas grasslands of New Mexico.
Full to part sun, best on irrigation in low desert.
Photo by Sue Carnahan, iNaturalist
Bouteloua radicosa on SEINET
Many bee species collect the pollen of many species of grasses. All can be used for desert tortoise enclosures, though the more spreading types are better for keeping up with a tortoise appetite. All grasses provide as larval hosts to many grass generalist Lepidoptera, especially species of skippers.
Grasses also play an important role in the ecology of soil, and because they are monocots, they can be planted close to other species of plants (the nature of the root systems of monocots renders them less imposing on neighboring plants). They hold soil down and help prevent erosion. Many species are pioneer plants that convert disturbed soils into hospitable places for other plants.
Bouteloua named for brothers Claudio (1774-1842) and Esteban (1776-1813) Boutelou Agraz, Spanish botanists and horticulturalists; radicosa has a fuzzy translation but most likely belonging to, pertaining to, or affecting roots; characterized by the presence of radicles. There are 57 species of Bouteloua found only in the Americas, with most diversity centered in the southwestern United States.
Found on dry rocky slopes; 3,500-7,000 ft. in southern Arizona, southern New Mexico; south into southern Mexico. It has also become established in Maine, growing in disturbed habtiats, but is not common there.
Floral detail, photo by Moises Perez, iNaturalist
When the floral spikes first emerge, they have a purple hue which lends their common name, purple grama. Photo by Moises Perez, iNaturalist