Deer brush (Ceanothus integerrimus var. macrothyrsus) is a woody shrub in the Rhamnaceae or Buckthorn family. It is one of two varieties of deer brush, an unusual ceanothus that may be deciduous in winter.  The color of the flowers varies from white to blue or even pink. Its natural habitat is mixed conifer forest at 2,000 feet elevation,  primarily in California, including the Klamath Ranges, North Coast Ranges, Cascade Range, Sierra Nevada, Transverse Ranges, Peninsular Ranges, South Coast Ranges, San Francisco Bay and Modoc Plateau.

Deer brush performs best at high elevations and is particularly suited to growing in the shade of conifers or oaks. It is drought-adapted and prefers fast draining soil.  

Deer brush is browsed by wildlife, especially deer, and attracts butterflies, moths and other pollinators.