Peninsular Ranges of San Diego and Riverside County [1].
Five occurrences on Conserved Lands in MUs 8 (BLM, Margarita Peak, Rock Mountain Preserve, Santa Margarita River Park) and 9 (Cleveland National Forest).
None [2].
Granitic outcrops and chaparral [1]. Elevation range is 150-800 meters.
Ericaceae family [3]. 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 [2]. Burl-forming and vigorous at resprouting [3].
Bloom period is December-March [2].
Produces large amount of fruits and readily establishes seedlings on sites disturbed by bulldozers or wildfires [3].
Development and agricultural conversion [2].
Flowers and fruits are often heavily infested with boring insects on the eastern edge of its range [3]. A. rainbowensis is the only Arctostaphylos species throughout most of its range.
[1] Parker, V. T., M. C. Vasey, and J. E. Keeley 2016. Arctostaphylos rainbowensis, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=76574, accessed on September 07, 2016
[2] CNPS, Rare Plant Program. 2016. Inventory of Rare and Endangered Plants (online edition, v8-02). California Native Plant Society, Sacramento, CA. http://www.rareplants.cnps.org, accessed 07 September 2016.
[3] Keeley, J. E., and A. Massihi. 1994. “Arctostaphylos Rainbowensis, a New Burl-Forming Manzanita from Northern San Diego County, California.†Madroño. Los Angeles, CA.