Narrowleaf Willow

It is a deciduous shrub reaching 4–7 metres (13–23 ft) in height, exceptionally 7.6 m (25 ft) spreading by basal shoots to form dense clonal colonies. The leaves are narrow lanceolate, 4–12 centimetres (1+1⁄2–4+3⁄4 in) long and 2–10 millimetres (1⁄16–3⁄8 in) broad, green, to grayish with silky white hairs at least when young; the margin is entire or with a few irregular, widely spaced small teeth. The flowers are produced in catkins in late spring, after the leaves appear. It is dioecious, with staminate and pistillate catkins on separate plants, the male catkins up to 10 cm (4 in) long, the female catkins up to 8 cm (3 in) long. The fruit is a cluster of capsules, each containing numerous minute seeds embedded in shiny white silk.

The male flowers provide pollen for bees. It is a larval host to the California hairstreak, Lorquin's admiral, mourning cloak, sylvan hairstreak, tiger swallowtail, and viceroy.

This willow has many uses for Native Americans; the branches are used as flexible poles and building materials, the smaller twigs are used to make baskets, the bark is made into cord and string, and the bark and leaves have several medicinal uses. The Zuni people take an infusion of the bark for coughs and sore throats. The foliage is browsed by livestock.

Salix exigua is cultivated as an ornamental tree. In the UK it has gained the Royal Horticultural Society's Award of Garden Merit.