Mexican cliffrose

Description

Purshia mexicana is a species of perennial flowering small tree in the rose family known by the common name Mexican cliffrose. It is native to western-northern Mexico, the region of the Sierra Madre Occidental cordillera. Purshia stansburyana, native to the southwestern United States, has sometimes been included within P. mexicana. In its mostly mountainous, or higher elevation habitat, it grows in woodlands, desert, and plateau habitat. Stenophyllanin A, a tannin, can be found in P. mexicana. The range of Mexican cliffrose is from the western Mexican Plateau in the south, and the southern Sierra Madre Occidental cordillera north to a small region of northwest Sonora; it has a continuous range in the cordillera from Chihuahua south through Durango and Zacatecas, all mostly north of the Trans-Mexican Volcanic Belt, though a few scattered locales do occur in the belt. The plant is browsed by deer, cattle, and sheep, and is particularly important to these species during the winter. Native Americans made ropes and clothing from the bark, and fashioned arrow shafts from the stems. Purshia (bitterbrush or cliff-rose) is a small genus of 5-8 species of flowering plants in the family Rosaceae, native to western North America, where they grow in dry climates from southeast British Columbia in Canada south throughout the western United States to northern Mexico. The classification of Purshia within the Rosaceae has been unclear. The genus was originally placed in the subfamily Rosoideae, but is now placed in subfamily Dryadoideae. They are deciduous or evergreen shrubs, typically reaching 0.3–5 m tall. The leaves are small, 1–3 cm long, deeply three- to five-lobed, with revolute margins. The flowers are 1–2 cm diameter, with five white to pale yellow or pink petals and yellow stamens. The fruit is a cluster of dry, slender, leathery achenes 2–6 cm long. The roots have root nodules that host the nitrogen-fixing bacterium Frankia. The evergreen species were treated separately in the genus Cowania in the past; this genus is still accepted by some botanists.