The desert's sub-regions include the Colorado Desert of southeastern California; and the Yuma Desert east of the north-to-south section of the Colorado River in southwest Arizona. In the 1957 publication, Vegetation of the Sonoran Desert, Forrest Shreve divided the Sonoran Desert into seven regions according to characteristic vegetation: Lower Colorado Valley, Arizona Upland, Plains of Sonora, Foothills of Sonora, Central Gulf Coast, Vizcaíno Region, and Magdalena Region. Many ecologists now consider Shreve's Vizcaíno and Magdalena regions, which lie on the western side of the Baja California Peninsula, to be a separate ecoregion, the Baja California desert.
Many plants not only survive, but thrive in the harsh conditions of the Sonoran Desert. Many have evolved to have specialized adaptations to the desert climate. The Sonoran Desert's biseasonal rainfall pattern results in more plant species than in the other North America deserts. The Sonoran Desert includes plant genera and species from the agave family, palm family, cactus family, legume family, and numerous others.
Sonoran Desert near Tucson, Arizona, in winter (December)
The Sonoran is the only place in the world where the famous Saguaro cactus (Carnegiea gigantea) grows in the wild. Cholla (Cylindropuntia spp.), beavertail (Opuntia basilaris), hedgehog (Echinocereus spp.), fishhook (Ferocactus wislizeni), prickly pear (Opuntia spp.), night blooming cereus (Peniocereus spp.), and organ pipe (Stenocereus thurberi) are other species of cacti found here. Cactus provides food and homes to many desert mammals and birds, with showy flowers in reds, pinks, yellows, and whites—blooming most commonly from late March through June, depending on the species and seasonal temperatures.
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