Salix (willows). Only three species of Salix trees are native, S. amygdaloides, S. nigra and S. bebbiana. Four other species are aliens. The commonest large tree willow is S. fragilis, a naturalized species from Europe, often misidentified as S. nigra. Weeping willow, Salix babylonica seldom or never escapes, but people are fond of planting it in wet areas along lakes and streams where its origin may be difficult to determine. In addition to the 7 tree species noted here, there are 17 species of Salix shrubs reported for Wisconsin.

Characters in the following key are based mainly on Voss, vol 2.