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]

RHAMNUS

BUCKTHORN

Shrub, small tree
Stem: branches alternate, flexible; twigs sometimes thorn-tipped
Leaves sometimes clustered on short-shoots, deciduous or evergreen, petioled; stipules deciduous; blade 1-ribbed from base, entire or not
Inflorescence: umbel or flowers solitary, axillary
Flower bisexual or unisexual, generally < 3 mm; hypanthium at base fused to, developing around ovary in fruit, above base deciduous; sepals 4 or 5; petals 0, 4, or 5; stamens 4 or 5; ovary appearing partly inferior, chambers 2–4, each 1–2-ovuled, style lobes 2–4
Fruit: drupe, 2–4-stoned
Species in genus: 125 species: temp, few tropical
Etymology: (Greek: name for plants of this genus)
Reference: [Wolf 1938 Rancho Santa Ana Bot Gard Monogr 1]
Some of value in medicine or as dyes.

Native

R. rubra Greene

SIERRA COFFEEBERRY

Shrub < 2 m
Stem: bark red to bright gray; twigs red to gray; terminal bud not covered with scales, hairy
Leaves deciduous; petiole 2–12 mm; blade 15–80 mm, narrowly elliptic to obovate, thin, green or gray, base, tip acute to rounded, margin finely toothed to entire, surfaces glabrous to finely hairy, veins not prominent
Inflorescence 6–15-flowered; pedicels 1–12 mm
Flower bisexual; hypanthium 2 mm; sepals 5; petals 5; style included
Fruit 2-stoned, 12 mm, black
Ecology: Chaparral, montane forests, sagebrush steppe
Elevation: 1000–2200 m.
Bioregional distribution: Klamath Ranges, High North Coast Ranges, Cascade Range, n&c High Sierra Nevada, Modoc Plateau
Distribution outside California: Nevada
Several vars. distinguished with difficulty: var. rubra (leaf green; n SNH), grading into var. modocensis C. Wolf (leaves on short-shoots; MP); var. nevadensis (Nelson) C. Wolf (fruit pear-shaped; w NV); var. obtusissima (Greene) C. Wolf (leaf obovate; KR, CaR); var. yosemitana C.Wolf (leaf finely hairy; cSNH)
Horticultural information: DRN, SUN: 1, 2, 3, 4, 5, 6, 15, 16 &IRR: 7.