Species distinguishing characteristics:
- Deciduous shrub or small tree, 2–12 m tall
- Leaves with smooth margins that are usually widest above the middle
- Silky, female catkins with dark brown bracts
- Hairy, beak-like capsules
- Pointed stipules often fall off early in the season
- Velvety, hairy, young twigs
- Found at all elevations in dry to moist areas
- Can be difficult to identify with certaintyErect, deciduous shrub or small tree, 2–12 m tall (up to 20 m in tree-like specimens), with multiple woody, stems.
- Trees and shrubs (or dwarf shrubs) often in moist, early successional areas
- Tiny flowers in male and female catkins on separate plants
- Seed capsules with tiny, hair-tufted seeds
- Simple, alternate leaves with paired stipules at the base of the leaf stalk
- Family members include cottonwoods and aspens (Populus spp.)
Erect, deciduous shrub or small tree, 2–12 m tall (up to 20 m in tree-like specimens), with multiple woody, stems.
Leaves and stems:
Erect, woody branches with flexible bases that have alternate, stalked leaves. A pair of small, pointed, leaf-like stipules (or wing-like appendages at the base of each leaf stalk) often fall off early in the season. Velvety, leaf stalks, 0.5–1 cm long, lack glandular dots at the top. Leaves are narrowly oval- to egg-shaped, 3–10 cm long and 1–4 cm wide (usually widest above the middle), with wedge-shaped bases and round or pointed tips. Leaf margins are smooth or have a few round teeth near the tips, and are moderately to strongly rolled. The upper leaf surface is dark green and shiny with a hairy midvein or is sparsely covered with long, soft hairs. The lower leaf surface texture varies from sparse- to densely-covered in short, stiff, rust-colored or white hairs to smooth, pale and waxy. Bud scales between the leaf stalk and the twig are cylindrical and blunt tipped.
Young twigs are yellowish-green to dark reddish-brown with dense velvety to sparse woolly hair. Bark on older stems is smooth, gray or grayish-brown, shallowly fissured, and scaly.
Tiny flowers in dense, fuzzy cylindrical clusters, called catkins, emerge on the previous year’s branches before leaves. Male (pollen) and female (seed) catkins, found on separate plants, have short-stalks, 0.3–1 cm long, or are stalkless in short, leafy branchlets. Bracts below the flowers are dark brown to black and are covered in straight, silky hairs. Female catkins, 2–6 cm long, are densely silky, have 1 hairy ovary, styles (tubular portion of a female organ) that are 0.2–0.6 mm long, and stigmas (tip of a female organ) that are often twice as long as styles. Male catkins, 2–4 cm long, are pale yellow, fluffy, and have 2 stamens (pollen organs). Plants growing in the shade often fail to flower.
Hairy capsules, 5–8 mm long, that narrow to a beak-like point with 2 stigmas at the tip and form in female catkins. Capsules contain numerous tiny seeds that are surrounded by a tuft of silky hairs. At maturity, the capsules split open to release the wind-dispersed seeds.
Dry to moist thickets, seepage areas, open forests, gravel bars, riparian areas, and wetlands at low to subalpine elevations. Thrives in areas where it can establish from wind-carried seeds or by re-sprouting from deep roots such as clearings, recently burned areas, and avalanche slopes that are in early stages of succession. Unlike most willows (Salix spp.), it can grow in shade or on soils that are far from water.
Like other willows (Salix spp.), Scouler’s willow grows fast and produces large quantities of nutritional forage. Livestock, native ungulates (including deer (Cervidae spp.), elk (Cervus elaphus), and moose (Alces alces)), bears (Ursus spp.), snowshoe hares (Lepus americanus), porcupines (Erethizontidae spp.), beavers (Castor canadensis) and ptarmigans (Lagopus spp.) browse leaves, twigs, and bark. Beavers cut willows to expand the size of their wetland habitats, as well as to eat their bark, and the resulting shoots often take root in dams. The male pollen catkins offer a nutritious food for bees (Apoidea spp.), and other mammals such as moose (Alces alces) and bears (Ursus spp.).
Scouler’s willow may provide cover needed to aid in the re-establishment of conifer seedlings in disturbed areas. When it reaches high densities, however, Scouler’s willow may outcompete shade-intolerant conifers such as ponderosa pine (Pinus ponderosa).
Like other willows, the bark of Scouler’s willow is used medicinally as a pain-reliever, anti-inflammatory, astringent, and diuretic. It contains three phenol glycosides from which aspirin was originally derived: populin, salicin, and methyl salicylate. A tea of the bark can treat fevers, headaches, arthritis, and other inflammations (such as urinary tract infections), but its bitter, tannic nature make it hard to drink the tea in enough quantity to be effective. A strong tea of leaves can be used as a slightly weaker alternative. Externally, a strip of the bark can be tied over a cut as a band-aid that stops bleeding, inhibits bacterial growth, and draws out inflammation.
Many Native American tribes twisted the bark to make twine, fishing nets, and tumplines for carrying loads with the forehead. It was strong when wet but brittle when dry.