Flora of North America species comparison

Subspecies 6 (6 in the flora).

Frangula californica grows throughout most of California, and the subspecies are more or less separated geographically, but intermediates exist among all the subspecies except subsp. ursina (C. B. Wolf 1938). In California, subsp. ursina occurs only in eastern San Bernardino County. Subspecies californica is the most coastal, growing from the western Klamath Mountains south to the Agua Tibia Mountain in southern California. Subspecies occidentalis is characteristic of mafic and ultramafic substrates in northwest California; plants on other substrates approach subsp. californica, but leaf blades are equally green (not yellow-green) on both surfaces. Wolf reported that a form of R. californica found abundantly from the San Francisco Bay region to Santa Barbara County has leaves that are whitened beneath, but the hairs are much shorter than in subsp. tomentella. Plants in Los Angeles and Orange counties have leaf blades with sparse (not dense) tomentum and a few long hairs beneath as in subsp. cuspidata. Intermediates between subspp. crassifolia and tomentella are rare in northern California, but many plants in San Diego County that Wolf considered subsp. tomentella have narrowly to broadly elliptic leaf blades, thus resembling subsp. crassifolia in the Inner Coast Range.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

When present, the strongly revolute leaf margins of subsp. cuspidata contrast with those of other taxa of Frangula californica. Plants identifiable as subsp. cuspidata but with flat-margined leaves perhaps show the influence of subsp. tomentella.

(Discussion copyrighted by Flora of North America; reprinted with permission.)