About Muhlenbergia microsperma (DC.) Kunth
Muhlenbergia microsperma (DC.) Kunth is an annual or perennial tufted grass, with culms reaching 10 to 80 cm (3.9 to 31.5 in) in height. Its leaf blades measure 2 to 6 cm (0.79 to 2.36 in) long and 1 to 2.5 mm (0.039 to 0.098 in) wide. Leaf sheaths are most often shorter than the stem internodes, are glabrous, and have a smooth or minutely scabrous texture. The ligules are 1 to 2 mm (0.039 to 0.079 in) long, are decurrent to the sheath, and have a truncate to obtuse toothed tip. The main inflorescence is a purplish panicle that is 6.5 to 13.5 mm (0.26 to 0.53 in) long and 1 to 6.5 mm (0.039 to 0.256 in) wide, with spreading or ascending branches. A defining characteristic of this species is the presence of additional panicles holding 1 to 3 cleistogamous florets in the axils of the lower stem leaves. Its spikelets hold glumes 0.4 to 1.3 mm (0.016 to 0.051 in) long, and lemmas that are typically 2.5 to 3.8 mm (0.098 to 0.150 in) long. This species shows notable morphological diversity between and within its populations, and has a variable chromosome count of 2n = 20, 40, 60. Muhlenbergia microsperma is native to the Americas. In the United States, it occurs in the states of Arizona, California, Nevada, and Utah. It is widespread across Mexico, where it is native to Aguascalientes, Baja California, Baja California Sur, Chiapas, Coahuila, Mexico City, Durango, Guanajuato, Hidalgo, Jalisco, Mexico, Michoacán, Morelos, Nayarit, Nuevo León, Oaxaca, Puebla, Queretaro, San Luis Potosí, Sinaloa, Sonora, Tamaulipas, Tlaxcala, Veracruz, and Zacatecas. It is also native to Guatemala, and in South America it is found in Bolivia, Colombia, Ecuador, Peru, and Venezuela. This species grows in a wide range of habitats. It generally favors open areas and moderately to heavily disturbed sites such as roadsides, but can also grow in drainages, sandy slopes, cliffs, and rock outcrops. In North America, it most often occurs in creosote scrub, thorn-scrub forest, sarcocaulescent desert, and oak-pinyon woodland associations, at elevations ranging from 0 to 2,400 m (0 to 7,874 ft). It is also found in chaparral and coastal sage scrub habitats.
