Peninsular Ranges of San Diego and Riverside County .
Five occurrences on Conserved Lands in MUs 8 (BLM, Margarita Peak, Rock Mountain Preserve, Santa Margarita River Park) and 9 (Cleveland National Forest).
Granitic outcrops and chaparral . Elevation range is 150-800 meters.
Ericaceae family . Previously called A. peninsularis ssp. peninsularis or considered a hybrid of A. glandulosa and A. glauca. Possibly hybridization with A. glandulosa at the edge of the A. rainbowensis range.
Perennial evergreen shrub . Burl-forming and vigorous at resprouting .
Bloom period is December-March .
Produces large amount of fruits and readily establishes seedlings on sites disturbed by bulldozers or wildfires .
Development and agricultural conversion .
Flowers and fruits are often heavily infested with boring insects on the eastern edge of its range . A. rainbowensis is the only Arctostaphylos species throughout most of its range.