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Arctostaphylos rainbowensis

J. E. Keeley & A. Massihi

Rainbow Manzanita

G2Imperiled (G2G3) Found in 1 roadless area NatureServe Explorer →
G2ImperiledGlobal Rank
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.131451
Element CodePDERI042T0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderEricales
FamilyEricaceae
GenusArctostaphylos
Concept Reference
Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.
Taxonomic Comments
Described in 1994; accepted by Kartesz (1999). Some of the southern California reports of A. peninsularis are instead this species (Skinner and Pavlik 1994, CNPS; Simpson et al. 1998, for San Diego County; Beauchamp 1986).
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-04-11
Change Date2025-04-11
Edition Date2025-02-17
Edition AuthorsMaybury, K.; rev. B. MacBryde, 9/2000., L. Oliver (2003), A. Treher (2012), rev. Johnson, J. (2025)
Threat ImpactHigh
Range Extent1000-5000 square km (about 400-2000 square miles)
Number of Occurrences21 - 80
Rank Reasons
Arctostaphylos rainbowensis is a large shrub endemic to a small area of southern California, United States. While it is locally plentiful and apparently resistant to natural disturbances, many of the known sites have been converted to avocado orchards or residential developments and populations at some sites are declining for unknown reasons.
Range Extent Comments
Arctostaphylos rainbowensis is found in northwest San Diego and southwest Riverside counties, California, U.S.A. Range extent was estimated to be 1300 square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 2004 and 2025 (RARECAT 2024, GBIF 2025, iNaturalist 2025, NatureServe 2025, SEINet 2025, CNDDB 2025).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are 56 occurrences rangewide and an additional 15 historic occurrences observed between 1960 and 2004 (RARECAT 2024, GBIF 2025, iNaturalist 2025, NatureServe 2025, SEINet 2025).
Threat Impact Comments
Many occurrences are threatened either by the development of land into avocado orchards or other types of agricultural land or residential development (CNPS 2001 and CNDDB 2025). On the eastern edge of its range, the flowers and fruits are often heavily infested with boring insects and it is sympatric with A. glandulosa and hybridization and introgression may be occurring (Keeley and Massihi 1994). Some localized threats include recreation (humans, horses, dog-walking), non-native species, and fire (CNDDB 2025). An increase in large wildfires in southern California due to climate change will increase the likelihood of killing mature plants but the species is known to recolonize disturbances readily (Keeley and Massihi 1994.)
Ecology & Habitat

Habitat

Arctostaphylos rainbowensis grows in the coastal range chaparral dominated by exposed bedrock and very large boulders of acidic igneous rock and granite (Keeley and Massihi 1994, FNA 2009).

Reproduction

Arctostaphylos rainbowensis readily establishes seedlings on disturbed sites created either by wildfires or, more commonly, by bulldozers (Keeley and Massihi 1994.)
Terrestrial Habitats
Shrubland/chaparral
Other Nations (1)
United StatesN2
ProvinceRankNative
CaliforniaS2Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentLarge (31-70%)Extreme or 71-100% pop. declineHigh (continuing)
1.1 - Housing & urban areasLarge (31-70%)Extreme or 71-100% pop. declineHigh (continuing)
2 - Agriculture & aquacultureRestricted (11-30%)Extreme or 71-100% pop. declineHigh (continuing)
2.1 - Annual & perennial non-timber cropsRestricted (11-30%)Extreme or 71-100% pop. declineHigh (continuing)
3 - Energy production & miningSmall (1-10%)Serious or 31-70% pop. declineHigh (continuing)
3.2 - Mining & quarryingSmall (1-10%)Serious or 31-70% pop. declineHigh (continuing)
4 - Transportation & service corridorsSmall (1-10%)UnknownHigh (continuing)
4.1 - Roads & railroadsSmall (1-10%)UnknownHigh (continuing)
6 - Human intrusions & disturbanceRestricted (11-30%)UnknownHigh (continuing)
6.1 - Recreational activitiesRestricted (11-30%)UnknownHigh (continuing)
6.3 - Work & other activitiesRestricted (11-30%)UnknownHigh (continuing)
7 - Natural system modificationsRestricted (11-30%)UnknownUnknown
7.1 - Fire & fire suppressionRestricted (11-30%)UnknownUnknown
8 - Invasive & other problematic species, genes & diseasesRestricted (11-30%)UnknownHigh (continuing)
8.2 - Problematic native species/diseasesRestricted (11-30%)UnknownHigh (continuing)

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Plant Characteristics
DurationPERENNIAL, EVERGREEN
Economic Value (Genus)No
Roadless Areas (1)
California (1)
AreaForestAcres
San Mateo CanyonCleveland National Forest65
References (13)
  1. Beauchamp, R.M. 1986. A flora of San Diego County, California. Sweetwater River Press, California. 241 pp.
  2. California Department of Fish and Game. 2000. Natural Diversity Database (RareFind 2), Version 2.1.2, January 25, 2000. Downloaded in 2003.
  3. California Native Plant Society (CNPS). 2001. Inventory of Rare and Endangered Plants of California (sixth edition). Rare Plant Scientific Advisory Committee, David P. Tibor, Convening Editor. California Native Plant Society. Sacramento, CA. x + 388pp.
  4. California Natural Diversity Database (CNDDB). 2012. RareFind Version 4 with dataset 9/1/2012 downloaded from http://www.dfg.ca.gov/biogeodata/cnddb/rf_ftpinfo.asp. California Department of Fish and Game, Sacramento.
  5. California Natural Diversity Database (CNDDB). 2025. RareFind Version 5.3.0. California Department of Fish and Game, Sacramento.
  6. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  7. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  8. Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.
  9. Keeley, J.E., and A. Massihi. 1994. Arctostaphylos rainbowensis, a new burl-forming manzanita from northern San Diego County, California. Madrono 41(1): 1-12.
  10. NatureServe. 2025. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  11. NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2024. Version: 1.1.1 (released Oct 01, 2024).
  12. Simpson, M.G., S.C. McMillan, B.L. Stone, J. Gibson, and J.P. Rebman. Checklist of the vascular plants of San Diego County. 2nd edition, 3rd printing. San Diego State Univ. Herbarium Press, San Diego, California. 87 pp.
  13. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).