Salix nigra may take the form of a shrub or a tree, with simple, alternate, finely toothed leaves. The leaves are green on both surfaces and stipules are usually present. The willow species are difficult to distinguish and any "shortcuts" around the proven keys are likely to result in frequent errors. The keys in Michigan Flora, Vol. 2 are recommended.

Salix nigra is near the northwestern limit of its distribution in Wisconsin and is found mostly in the southern part of the state. It becomes established on wet, sunny sites (which may subsequently grow up into forest) and is often associated with streams. It is short-lived, apparently reaching an age of 70-85 years.