Ceanothus greggii

Ceanothus greggii, known by the common name desert ceanothus, is a species of flowering shrub in the buckthorn family, Rhamnaceae. It is native to the Southwestern United States (Arizona, California, New Mexico, Texas, and Utah) and northern Mexico, where it grows primarily in desert scrub, sagebrush, chaparral, and other dry habitats such as inland mountain slopes, at elevations of to .
It was named by Asa Gray of Harvard University in 1853 in honor of its collector, Josiah Gregg, who found the plant in 1847 at the site of the Battle of Buena Vista in the Mexican state of Coahuila during the Mexican–American War. 
Description.
"Ceanothus greggii" is a many-branched shrub that grows erect to nearly in maximum height. Its woody parts are gray in color and somewhat woolly. Branches are opposite and rigid. The evergreen leaves are oppositely arranged, 2–9 mm 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).
The inflorescence is a small (less than 2 cm long) cluster of many white flowers on short lateral branches. The flowers bloom in spring. Blooms are considered highly fragrant. The fruit is a horned capsule a few millimeters wide which bursts explosively to expel the three seeds inside, which require thermal scarification from wildfire before they can germinate.
"C. greggii" is eagerly browsed by livestock and wild ungulates such as mule deer and desert bighorn sheep.
Varieties.
Distinct varieties of "C. greggii" include: