RHAMNACEAE

BUCKTHORN FAMILY

John O. Sawyer, Jr. (except Ceanothus)

Shrub, vine, tree, generally erect, often thorny
Leaves simple, generally alternate, often clustered on short-shoots, generally petioled, generally stipuled; blade often 1–3-ribbed from base
Inflorescence: cyme, panicle, or flowers solitary in axils
Flower generally bisexual, radial; hypanthium subtending, surrounding, or partly fused to ovary; sepals 4 or 5; petals 0, 4, or 5, clawed; stamens 4 or 5, alternate sepals, attached to hypanthium top, each generally fitting into a petal concavity; ovary superior or partly inferior, chambers 2–5, each 1–2-ovuled, style lobes or parts 1–3
Fruit: capsule, drupe
Genera in family: 55 genera, 900 species: especially tropical, subtropical; some cultivated (Ceanothus ; Colletia , anchor-plant; Gouania ; Phylica ; Rhamnus ; Ventilago ; Ziziphus )
Reference: [Brizicky 1965 J Arnold Arbor 45:439–463]

CEANOTHUS

CALIFORNIA-LILAC

Clifford L. Schmidt

Shrub, small tree, prostrate to erect, thorny or not
Stem: branches generally arranged as leaves
Leaves alternate or opposite, deciduous or evergreen, petioled; blade 1–3-ribbed from base, margin entire or not
Inflorescence: generally panicle-like aggregations of umbel-like, 3-flowered clusters
Flower generally < 5 mm; hypanthium surrounding fleshy disk below ovary base, in fruit thick, not splitting; sepals generally 5, lanceolate-deltate, incurved, colored like petals, persistent; petals generally 5, hooded, white to deep blue; stamens generally 5, opposite petals; ovary superior, 3-lobed, chambers 3, each 1-ovuled, style parts 3
Fruit: capsule, ± spheric, 3-valved
Seeds 3, ± 3 mm, 1 surface convex
Species in genus: 45 species: North America, especially w
Etymology: (Greek: thorny plant)
Reference: [Rensselaer & McMinn 1942 Ceanothus Santa Barbara Bot Gard 1–308]
Hybridization common (named hybrids not recognized here); hybrid forms may not key adequately.

Native

C. integerrimus Hook. & Arn.

DEER BRUSH

Plant ascending-erect, < 4 m
Stem: twigs round, yellow- to pale-green, glabrous to ± strigose, not changing color
Leaves alternate, deciduous, < 8 cm; stipules deciduous; petiole < 15 mm; blade lanceolate, elliptic or ± oblong to widely ovate, 1–3-ribbed from base, thin, tip acute to obtuse, margin generally entire or minutely dentate toward tip, upper surface light green, ± glabrous to puberulent, lower paler, ± glabrous to hairy
Inflorescence ± raceme-like, < 15 cm, clusters generally stalked
Flower white or blue, rarely pink
Fruit 4–5 mm, sticky; top ± depressed; valves minutely crested
Chromosomes: 2n=24
Ecology: Dry slopes, ridges
Elevation: 300–2100 m.
Bioregional distribution: Klamath Ranges, North Coast Ranges, Cascade Range, Sierra Nevada, San Francisco Bay Area, South Coast Ranges, Transverse Ranges, Peninsular Ranges
Distribution outside California: to Washington
Several poorly defined vars. have been recognized: var. i. (leaf blade oblong to elliptic-oblong, generally 1-ribbed from base; flower white or blue; SnFrB, SCoR); var. californicus (Kellogg) G.T. Benson (leaf blade elliptic or lanceolate to oblong-ovate, 3-ribbed from base, upper surface generally glabrous, lower glabrous or hairy; flower white; KR, NCoR, CaR, SN); var. macrothyrsus (Torr.) G.T. Benson (leaf blades oblong to ovate, generally 3-ribbed from base, generally hairy on both surfaces; flower white to blue; KR, CaRH, to WA); var. puberulus (Greene) Abrams (leaf blade elliptic or lanceolate to oblong-ovate, 3-ribbed from base, generally hairy on both surfaces; flower white; TR, PR)
Horticultural information: DRN: 4, 5, 6, 15, 16, 17 &IRR: 1, 2, 3, 7, 14, 18, 19, 20, 21.