Distribution

Siltbush has been described as a "narrowly distributed edaphic endemic" [30]. Isolated populations occur in salt desert habitats in the Colorado River drainage from northwestern New Mexico and northeastern Arizona to Utah and the Colorado-Wyoming border. A single siltbush population occurs outside of this area, in the Great Basin west of Sterling, Utah [3,23,35,36]. Scattered Zuckia brandegeei var. arizonica populations occur in northern Arizona and southeastern Utah [30,40]. Zuckia brandegeei var. brandegeei occurs in northeastern Arizona, south-central Utah, and western Colorado, and Z. b. var. plummeri populations occur in northeastern Utah, south-central Wyoming, western Colorado, and northwestern New Mexico [10,30,40]. Flora of North America provides a distributional map of siltbush and its varieties.