Habit: low growing densely branched, evergreen with a flattened top. At higher elevations it is fast growing forming a large groundcover. The stems have smooth, grayish bark and thorns on the ends of the branches. Grayish green leaves are small and oval shaped with a rounded tip, margins can be smooth or with fine teeth. Flowers are densely clustered, white and appear fluffy and have a penetrating fragrance. The fruit are in a 3 lobed triangular capsule each containing a seed. Whitethorn blooms in late spring to mid summer.
Ecology: found in open woodlands and dry rocky slopes in the upper montane region of the Sierra Nevada as an understory plant of Sequoiadendron giganteum, Quercus kelloggii, Prunus emarginata occurring at elevations of 2100-11,000 ft (650-3350m).
Growing Conditions: shade to partial shade, coarse well-drained soil. Drought tolerant once established, cold hardy.
It has high nitrogen in its foliage and with the help of symbiotic bacteria has the ability to fix nitrogen. Important forage for deer and other wildlife.