Gutierrezia is a genus of roughly 25–30 species of flowering plants in the daisy family Asteraceae (order Asterales), native to arid and semi-arid regions of western North America and western South America. The genus was first described by the Spanish botanist Mariano Lagasca in 1816.
Plants in the genus are commonly known as snakeweeds or matchweeds, and a few species have historically been called greasewood. They grow as annuals, perennials, or small subshrubs, typically reaching 20–80 cm in height. The stems are often resinous and branched, bearing narrow leaves. The flowerheads are small and numerous, clustered near branch tips, and bear yellow (occasionally white) ray and disc florets in the typical composite arrangement of Asteraceae.
The genus spans a wide geographic arc: in North America, species occur from southern Canada and the western United States south through Mexico; in South America, populations are found in Chile and Argentina. Many species favor dry grasslands, shrublands, and disturbed ground, where they can become dominant after overgrazing or drought.
Several species — most notably G. sarothrae (broom snakeweed) and G. microcephala (threadleaf snakeweed) — are recognized as toxic to livestock, particularly sheep and cattle. The plants produce terpenoid and saponin compounds that can cause abortion in pregnant animals and liver damage with prolonged exposure, making them economically significant range weeds across the southwestern United States and Mexico. Despite their toxicity to livestock, snakeweeds have been used medicinally by various Indigenous peoples of the American Southwest.
Etymology
The genus name Gutierrezia honors Pedro Gutierrez, a Spanish botanist of the early nineteenth century. The genus was established by Mariano Lagasca in 1816 in his Genera et Species Novarum. Common names — snakeweed, matchweed, and greasewood — reflect the plants' resinous, wiry stems and their association with disturbed or overgrazed land.
Distribution
Gutierrezia has a disjunct native range spanning western North America and western South America, with no presence in the intervening tropics. In North America, species occur from the southern prairies of Canada south through the Great Plains, the Intermountain West, and the southwestern United States into Mexico (including Baja California, Sonora, Chihuahua, and states further south). South American populations are concentrated in the arid Andes foothills and coastal ranges of Chile and Argentina. The genus is largely absent from humid or tropical zones.
Ecology
Most Gutierrezia species are characteristic plants of open, dry grasslands, desert scrub, and shrub-steppe communities. They are well adapted to semi-arid conditions and can dramatically increase in abundance following overgrazing, drought, or other disturbance that reduces grass cover — making G. sarothrae one of the most visible range-management weeds in the western United States. The plants are visited by a range of small insects. Terpenoid and saponin compounds in the foliage are believed to deter browsing and contribute to their competitive success in degraded rangelands.
