This section is from the "The Herb Hunters Guide" book, by A. F. Sievers. Also available from Amazon: Herb Hunters Guide.

Figure 19.Black willow (Salix nigra)
Swamp willow.
This tree is found in low ground and along streams from New Brunswick to western Ontario and in North Dakota, Florida, and Texas.
This willow is a tree attaining a height of 120 feet and a trunk diameter of 3 feet, with narrow lance-shaped leaves 2 1/2 to 5 inches long and up to three-quarters of an inch wide, finely toothed and hairy when young. Male and female flowers are borne in separate catkins which expand with the leaves the male catkins l to 2 inches and the female catkins 1 1/2 to 3 inches long.
The bark and buds.
 
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