SALICACEAE

WILLOW FAMILY

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.

SALIX

WILLOW

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.

Native

S. exigua Nutt.

NARROW-LEAVED WILLOW

Shrub < 7 m, clonal by root-sprouting
Stem: twigs brownish, silky or long-soft-wavy-hairy, becoming glabrous
Leaves: stipules 0 or vestigial; petiole short; young leaves silky; mature blade 50–124 mm, linear, acuminate (base wedge-shaped), entire to sharply serrate (teeth well separated), silky, glaucous below or not
Inflorescence appearing with or after leaves, sometimes branched, 22–70 mm, on leafy shoots 5–110 mm; flower bract tawny; pistillate bract deciduous after flower
Staminate flower: stamens 2
Pistillate flower: ovary glabrous, silky, or sparsely soft-shaggy-hairy, stigma deciduous after flower, style 0–0.2 mm, stalk 0.2–1 mm
Chromosomes: 2n=38
Ecology: Common. Streamsides, marshes, wet ditches
Elevation: < 2700 m.
Bioregional distribution: California
Distribution outside California: to Alaska, e N.America, Arizona, Mexico
Flowering time: Mar–May
Synonyms: var. stenophylla (Rydb.) C.K. Schneid.; S. hindsiana Benth. including vars. leucodendroides (Rowlee) C.R. Ball and parishiana (Rowlee) C.R. Ball
Plants with spreading hairs on leaves and twigs, slender stigmas 0.6–1 mm, and ± entire leaves from throughout CA have been called S. hindsiana Benth.; these features vary independently; the type of S. h. Benth. does not share them all. Such forms may be derived from S. e. Nutt. X S. sessilifolia Nutt.; further study needed
Horticultural information: WET, SUN: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24; STBL.