Salix petrophila, commonly known as alpine willow and Rocky Mountain willow, is a Northwest American mountain shrub in the Willow Family (Salicaceae).
It can be found in the subalpine zone and alpine zone of the Sierra Nevada range in wetlands such as moist banks and wet meadows, up to 9,900 to 13,000 feet (3,000 to 4,000 m).
It is often overlooked because although sprawling and mat-forming, it is very small for a shrub, growing to only 4 inches (0.10 m) tall.
Leaves are 34 to 1 34 inches (0.019 to 0.044 m) long, elliptic, with soft hairs on the surface when young. The other mat forming Sierra Nevada alpine willow, Salix nivalis, has smaller leaves (14 to 78 inch (0.0064 to 0.0222 m) that are hairless when young.
Each plant has either all male or all female flowers, with an inflorescense that is a dense, upright catkin, growing to 2 inches (0.051 m).
It is pollinated by ants, as are some other willows.