Hemlock, an evergreen tree of the pine family. There are about 10 species, 4 of which are native to North America, the others to Asia. The hemlock is a pyramid-shaped tree with almost horizontal branches. Its flat, blunt needles appear in two rows, dark green above, lighter beneath. The bark is brownish or reddish brown.

The eastern hemlock, Canadian hemlock, or hemlock spruce grows from Canada south to Georgia and west to Wisconsin. It is the state tree of Pennsylvania. The tree varies from 60 to 100 feet (18 to 30 m) in height. Its lightweight wood is used for coarse lumber, its bark for leather tanning. The slightly shorter Carolina hemlock grows in the mountains from Virginia to Georgia. It is often used as an ornamental tree.

The mountain hemlock, which averages 90 feet (27 m) in height, grows in mountainous regions from Alaska to central California. It is widely grown as an ornamental tree. The western hemlock grows along the coast from Alaska to California. Largest of the hemlocks, it is about 200 feet (60 m) tall and has a trunk diameter of three to four feet (0.9 to 1.2 m). The wood is used for lumber, veneer, and pulpwood; the bark for tanning.

The eastern hemlock is Tsuga canadensis; Carolina, T. caroliniana; mountain, T. mertensiana; western, T. heterophylla.