Most of the North American willows are shrubby, but black willow is the most distinctive as a tree. It is a small to medium tree. On some sites it can reach heights of 90 feet, but it grows mostly to between 30 and 40 feet tall. It has a short trunk with a diameter of up to 3 feet. The crown is spreading and is usually rounded, but can be open and irregular.
Black willow occurs in every county in Illinois on wet ground, most commonly along rivers and streams. It is widespread throughout the entire eastern United States with the exception of Florida, from which it is absent. Its spreading, shallow roots need a continuous supply of moisture throughout the growing season, and it is most abundant on floodplains and in swamps and sloughs. It occurs in pure stands in floodplains throughout its range.
Black willow cannot grow well in shade. Its seeds must germinate within a day or two after they are shed. They are dispersed by wind and water, and they are often deposited along streams and on sand bars, where they grow into pure even-aged stands.
Black willow wood is light-weight, soft and weak. It is used for pulpwood, charcoal, flooring, boxes and crates, and veneer. It was once used for artificial limbs because of its light weight and the fact that it glued well and is easily worked with tools. Glucoside salicin, the original basic ingredient of aspirin, was extracted from the leaves and bark of the tree in the early 19th century. Today the chemical (salicylic acid) is synthesized rather than extracted.