Taxon Report

Quercus tomentella Engelm.

island oak

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Taxon Summary

Quercus tomentella, commonly known as island oak, is a perennial evergreen tree in the Fagaceae that is found in California and elsewhere. It occurs within Chaparral, Cismontane woodland, Closed-cone coniferous forest, and Riparian woodland, growing at elevations from 15 to 730 meters. Quercus tomentella is ranked 4.2, Plants of Limited Distribution, A Watch List; Moderately threatened in California.

Classification


Scientific Name:	Quercus tomentella Engelm.
Common Name:	island oak
Family:	Fagaceae
Element Code:	PDFAG05250
USDA Plants Symbol:	QUTO
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial evergreen tree
Blooming Period: Mar-Jul	Mar-Jul
Elevation:	15-730 (50-2395)
General Habitats:	Chaparral, Cismontane woodland, Closed-cone coniferous forest, Riparian woodland
Microhabitat:
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	4.2
Global Rank:	G3G4
State Rank:	S3S4
State List:	None
Fed List:	None
Other Status:	IUCN_EN; SB_CRES
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	0
Element Occurrence Ranks:
Excellent (A)	0
Good (B)	0
Fair (C)	0
Poor (D)	0
None (X)	0
Unknown (U)	0

Location


California Endemic: False
California Counties and Islands: Name (Code)
Los Angeles (LAX), Santa Barbara (SBA), Ventura (VEN)
Quads: Name (Quad Code)
Anacapa Island (3311983), San Clemente Island Central (3211874), San Clemente Island North (3211885), San Clemente Island South (3211873), Santa Catalina East (3311833), Santa Catalina South (3311834), Santa Cruz Island A (3311987), Santa Cruz Island B (3311986), Santa Cruz Island C (3311985), Santa Rosa Island North (3312081), Santa Rosa Island South (3312071)

Threat List Data from the CNDDB


Threat List Total:	0
EOs with Threat Listed:	Total EOs	% of EOs
	0	0 %

Notes



Threatened by trampling, erosion, grazing, feral herbivores, and introgression. Hybridizes with Q. chrysolepis except on SRO and GU islands. Populations on GU Isl. have declined dramatically in recent years. See Transactions of the Academy of Science of St. Louis 3:393 (1877) for original description.
Threats:

Taxonomy:

Selected References

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 22 November 2025].