Jepson Flora Project: Jepson Interchange    

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Jepson Interchange (more information)
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  • Up-to-date information about California vascular plants is available from the Jepson eFlora.



Shrub, tree, generally dioecious (rarely monoecious)
Stem: trunk < 40 m; wood soft; bark smooth, bitter; buds scaly
Leaves simple, alternate, deciduous; stipules generally deciduous, often large
Inflorescence: catkin, generally appearing before leaves; each flower subtended by disk or 1–2 nectary glands and 1 bract
Flower: perianth 0
Staminate flower: stamens 1–many
Pistillate flower: pistil 1, ovary superior, chamber 1, stigma lobes 2–4
Seeds many; hairs fine, white, cottony
Fruit: capsule; valves 2–4
Genera in family: 2 genera, 340 species: generally temp (except Australia, Malay Archipelago) moist places; many cultivated. Hybridization common; identification often difficult. Family description, key to genera by John O. Sawyer, Jr.



George W. Argus

Shrub, tree, dioecious; bud scale 1, not sticky, margins generally fused (or free, overlapping)
Stem: twigs generally flexible and not glaucous
Leaf: blade linear to widely obovate, entire to toothed, generally ± hairy
Inflorescence: dense catkin emerging before, with, or after leaves, sessile or on a short leafy shoot; bract subtending each flower
Flower: perianth 0
Staminate flower: stamens 1–8
Pistillate flower: ovary stalked or sessile, style 1 or 0, stigmas 2, each sometimes 2-lobed; nectaries 1–several, generally rod-like, generally between inflorescence axis and flower
Fruit: valves 2
Species in genus: ± 400 species: ± worldwide, especially n temp, arctic
Etymology: (Latin: ancient name)
Reference: [Argus 1986 Syst Bot Monog 9:1–170; Dorn 1976 Canad J Bot 54:2769–2789]
Difficult, highly variable. Not all specimens will key easily; sprout shoots and other extreme forms are not included in keys, may require field comparison for identification. Studies of variation, hybridization needed.


S. alba L.


Tree < 25 m
Stem erect, spreading, or pendent; twigs yellowish to gray- or red-brown, sometimes ± brittle at base, silky, becoming glabrous
Leaves: stipules leaf-like; petiole with glands; young leaves silky; mature blade 63–115 mm, lanceolate to elliptic, acute (base acute or wedge-shaped), finely serrate, silky, becoming glabrous, lower surface glaucous, upper surface dull
Inflorescence appearing with leaves, 30–60 mm, on leafy shoot 3–25 mm; flower bract tawny, glabrous or sparsely hairy, tip rounded; pistillate bract deciduous after flower
Staminate flower: stamens 2; axillary and outer nectaries present
Pistillate flower: ovary glabrous, style ± 0.2 mm, stalk 0.2–0.8 mm
Chromosomes: 2n=76
Ecology: Disturbed places, generally near settlements
Elevation: generally < 1000 m.
Bioregional distribution: California
Distribution outside California: to e N.America; native to Europe
Mostly cultivated as ornamental, but many CVS and hybrids ± naturalized. Var. vitellina (L.) Stokes (twigs bright yellow or golden, spreading) and hybrids with S. fragilis L. most common.

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