Salix scouleriana (Scouler's willow; syn. S. brachystachys Benth., S. capreoides Anderss., S. flavescens Nutt., S. nuttallii Sarg., S. stagnalis Nutt.) is a species of willow native to western North America, from south central Alaska east to western Northwest Territory, central Manitoba, and the Black Hills of South Dakota, and south through the Rocky Mountains to Coahuila, and along the coast through British Columbia, Washington, Oregon, and the Sierra Nevada in California. Other names occasionally used include fire willow, Nuttall willow, mountain willow, and black willow. It is a deciduous shrub or small tree, depending on the environment, usually with multiple stems that reach 2 to 7 m in height in dry, cold, high elevations, and other difficult environments, and 10 to 20 m in favorable sites. The stems are straight and support few branches generally resulting in narrow crowns. The root system is fibrous, deep, and widespread. The thick sapwood is nearly white, and heartwood is light brown tinged with red. Stem bark is thin, gray or dark brown, with broad, flat ridges. Twigs are stout and whitish-green. The leaves are oblanceolate to elliptic, 5–12.5 cm long, mostly short-pointed at the apex and tapered toward the base, with entire to sparsely wavy-toothed margins. They are dark-green and nearly hairless above, and white- or grayish-hairy below. It is dioecious, having male and female flowers on different trees. The flowers are tiny, grouped in pussy willow-like catkins. The anthers, two per flower, are yellow, sometimes tipped with red; pistils are red. The fruit is light reddish-brown, long-pointed capsules about 0.75 cm long. At maturity, they open to release a white fluff with tiny, imbedded seeds. The species has 2n = 76 or 114 chromosomes.