The bark is dark brown to blackish, becoming fissured in older trees, and frequently forking near the base.

[3] The shoots are slender and variable in color from green to brown, yellow or purplish; they are (like the related European Salix fragilis) brittle at the base, snapping evenly at the branch junction if bent sharply.

The leaves are alternate, long, thin, 5–15 centimeters (2–6 in) long and 0.5–2 centimeters (1⁄4–3⁄4 in) broad, usually somewhat falcate, dark, shiny green on both sides or with a lighter green underside, with a finely serrated margin, a short petiole and a pair of small stipules.

The fruit is a 5 millimeters (3⁄16 in) capsule which splits open when mature to release the numerous minute, down-covered seeds.

[3] Salix nigra is native to a large portion of North America, from New Brunswick and southern Ontario west to California and Arizona, and south to northern Florida and Texas.

[4] Salix nigra grows best in areas of full sun and wet or moist soils.

After they germinate, they can experience excellent growth if they are exposed to high sunlight and copious moisture during the growing season.

Black willows living in drought conditions experience inhibition of their branch and root growth.

[19] Ethnobotanical uses of black willow by various Native American tribes include basketry, and treatment of fever, headache, and coughs.

Salix nigra is used for marshland stabilization or restoration projects as long as the roots don't penetrate any clay liner that may be in place.

[25] Photodegradation is theorized to work by drawing the target chemical, such as bentazon, up the roots and stem into the leaves where it is degraded by high-energy radiation provided by the sun.

When black willow are infected, the bacteria stimulate a quick burst in growth of plant cells.

However, these galls can cause a disruption in the flow of nutrients throughout the tree and can have its normal growth stunted or slowed down due to this disease.

This disease starts as spotting on the leaves of the black willow, where it then spreads to the petiole and eventually the twig or branch holding the leaf.

Tissue on the black willow that is affected by these cankers will not grow with the rest of the tree, and cracks will begin to form.