It is native to the Southwestern United States, California, New Mexico, Texas, and northern Mexico. It grows in desert scrub, sagebrush, chaparral, and other dry habitats such as inland mountai slopes, at elevations of 1,000 m (3,300 ft) to 2,300 m (7,500 ft) .
It was named for its collector Josiah Gregg, who found the plant in 1847 at the site of the Battle of Buena Vista in the state of Coahuila, in northern Mexico during the Mexican-American War by Asa Gray of Harvard University in 1853. 
Ceanothus greggii is a many-branched shrub that grows erect to nearly 2 m (6.6 ft) in maximum height. Its woody parts are gray in color and somewhat woolly. Branches are opposite and rigid.
The evergreen leaves are oppositely arranged, 2 to 9mm long, and variable in shape, with a prominent midvein. They may be toothed or smooth along the edges, and are indeed usually somewhat cupped (see top image).
- Ceanothus greggii var. franklinii — desert ceanothus, endemic to Grand and San Juan Counties, Utah. 
- Ceanothus greggii var. greggii — desert ceanothus
- Ceanothus greggii var. perplexans — Gregg's ceanothus
- Ceanothus greggii var. vestitus — Mojave ceanothus
- John D. Stuart, John O. Sawyer, Andrea J. Pickart (2001). Trees and Shrubs of California. University of California Press. ISBN 978-0-520-22110-9.
- Blakely, Larry, Desert Ceanothus, Ceanothus greggii A. Gray var. vestitus (E. Greene) McMinn (Rhamnaceae), Who's in a Name? People Commemorated in Eastern Sierra Plant Names
- Forest Service Fire Ecology
- USDA: Subordinate taxa of Ceanothus greggii
- ITIS Standard Report Page: Ceanothus greggii
- S.L. Welsh. New taxa and new nomenclatural combinations in the Utah flora. Rhodora. volume 95. 1993. 
Media related to Ceanothus greggii at Wikimedia Commons
- Calflora Database: Ceanothus greggii (desert ceanothus)
- Jepson Manual treatment of Ceanothus greggii
- USDA Plants Profile for Ceanothus greggii (desert ceanothus)
- UC Photos gallery — Ceanothus greggii
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