Gen. Amer. Bor. 2: 178. 1849.
Shrubs, 0.5–5 m. Stems red to gray or brown, glabrous or hairy. Leaves usually persistent, rarely deciduous; petiole 3–10 mm; blade bright green to green, gray-green, yellowish green, or yellow abaxially, dark green to yellowish green or greenish white adaxially, not glaucous, ovate, elliptic, or oblong-elliptic, 2–10 cm, distinctly coriaceous, base cuneate to rounded or subcordate, margins entire or serrate, serrulate, or dentate-serrulate, apex acute or acuminate to obtuse, rounded, or truncate, abaxial surface glabrate or densely and closely white stellate-hairy, adaxial surface glabrous, glabrate, or sparsely hirsutulous; secondary veins 7–11(–12) pairs. Inflorescences umbels, pedunculate, 5–60-flowered. Pedicels 10–20 mm. Stigmas 2–3-parted. Drupes black, globose or slightly elongate, 10–15 mm; stones 2–3.
Ariz., Calif., N.Mex., Nev., Oreg., nw Mexico, introduced in Pacific Islands (Hawaii).
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.
|1||Leaf blade surfaces glabrous or abaxial slightly puberulent; drupe stones 2–3.||> 2|
|2||Leaf blades bright green or yellow abaxially, dark green adaxially; drupe stones 2.||Frangula californica subsp. californica|
|2||Leaf blades yellowish green on both surfaces; drupe stones 3.||Frangula californica subsp. occidentalis|
|1||Leaf blade abaxial surface white stellate-hairy, sometimes with intermixed simple, erect hairs, adaxial surface glabrous, glabrate, sparsely hirsutulous, or sparsely stellate-hairy; drupe stones 2.||> 3|
|3||Leaf blade abaxial surfaces without simple, erect hairs.||> 4|
|4||Leaf blades narrowly elliptic, green and glossy adaxially, abaxial surfaces densely and closely white stellate-hairy, adaxial surfaces glabrous.||Frangula californica subsp. tomentella|
|4||Leaf blades broadly elliptic to oblong-elliptic, green to gray-green adaxially, both surfaces white stellate-hairy, sparsely so adaxially.||Frangula californica subsp. crassifolia|
|3||Leaf blade abaxial surfaces with simple, erect hairs, at least along veins.||> 5|
|5||Leaf blade apices abruptly acuminate to acute, margins sharply serrate to dentate-serrulate, sometimes strongly revolute.||Frangula californica subsp. cuspidata|
|5||Leaf blade apices acute to rounded, margins entire or serrulate to serrate, flat to slightly revolute.||Frangula californica subsp. ursina|