Grayleaf Willow

This willow is usually a shrub growing up to 1.2 m (3.9 ft) tall, but in appropriate habitat it becomes a tree up to 6 m (20 ft) tall. The smooth gray bark becomes furrowed with age. The species is dioecious, with male and female reproductive parts occurring on separate individuals. This species has secondary sexual dimorphism, with male and female individuals different in function or morphology in aspects other than their reproductive structures. For example, female plants are more sensitive to drought conditions. The seed stays on the plant until fall, when it is dispersed. The seed is coated in downy fibers that help it disperse on the wind and on water. Unlike the seeds of many other willows, these do not germinate immediately on contact with the substrate, but overwinter under the snow and sprout in the spring. This provides cold stratification to the seeds, and allows them a few weeks more to develop than in summer-dispersing willows.

In the northern part of its range, this plant codominates with other species of willow on floodplains and in shrubby riparian and tundra habitat. It may also grow scattered throughout coniferous forests and woodlands, dominated often by spruces. In the southern part of its range, it grows in alpine and subalpine climates. Like many other willows, it colonizes freshly cleared habitat, such as floodplains recently scoured by water and forests recently burned.

As with other willows, S. glauca is an important food source for a variety of animals, particularly wintering ungulates, providing them with a rich source of calcium and phosphorus. It is considered moderately important as moose browse, and during the winter it constitutes much of the diet for snowshoe hares.