This genus consists of about 400 species of deciduous
trees and shrubs. They are native primarily to the
cooler, temperate regions of the Northern Hemisphere. The
precursor to aspirin, salicylic acid, is found
in the bark and leaves of willows.
Most of the members of this genus
are trees but a few grow as shrubs. They tend to be fast growing
and weak wooded. The weeping willow is noted for its ability to
tolerate wet sites near ponds or streams.