Salix prolixa is a species of willow known by the common name MacKenzie's willow. It is native to western North America from Alaska and northwestern Canada to the high mountains of California and Utah. It grows in moist habitat such as riverbanks, springs, and marshes. It is a shrub growing 1 to 5 meters tall.
Habit: Shrub < 5 m. Stem: twigs yellow- or red-brown, glabrous or long-shaggy-hairy. Leaf: stipule leaf-like, tip convex to rounded; petiole 6--12 mm; young leaves glabrous or hairy; mature blade 50--150 mm, narrowly oblong or lanceolate to obovate, acuminate (base rounded to cordate), serrate to finely short-slender-serrate, abaxial hairs 0. Inflorescence: blooming with leaves, pistillate 19--66 mm, on leafy shoots 0.5--6 mm; flower bract brown, hairs wavy. Staminate Flower: stamens 2. Pistillate Flower: ovary glabrous, stalk 1.3--4.2 mm, style 0.3--0.7 mm.
Ecology: Banks of rivers, streams, marshes; Elevation: 110--2255 m. Distribution Outside California: to northern Canada, Wyoming. Flowering Time: Mar--Jun.It is a shrub growing 1 to 5 meters tall. The lance-shaped or pointed, oval leaves are up to 15 cm long, hairless, waxy on the undersides, and accompanied by wide stipules. The inflorescence is a catkin of flowers.