HEMLOCK, the name commonly given in North America to trees of the genus Tsuga, of the pine family (Pinaceae), corn prising nine species, five of which are native to eastern Asia and four to temperate North America. They are tall, pyramidal evergreen conifers, with cinnamon-red bark; slender, horizontal or somewhat drooping branches; fiat, narrowly linear, short stalked, two-ranked leaves and small, pendulous cones, with rounded, persistent, slightly woody scales.
The eastern hemlock (T. canadensis), called also Canada hemlock and hemlock-spruce, grows in upland forests from Nova Scotia to Minnesota and southward to Maryland, northern Indiana, south-western Wisconsin and in the mountains to Georgia and Alabama. It is a handsome tree, usually 6o to 8o ft. but sometimes 1 oo ft. high, with a trunk 2 to 4 ft. in diameter. The dark green leaves, 2 to a in. long, are grooved above and marked with two whitish bands beneath. The bark is valuable for tan ning and the soft, coarse-grained, splintery wood, though much inferior to pine or spruce, is extensively used for various building purposes. When young the eastern hemlock is one of the most ornamental of evergreens, and numerous varieties are in culti vation. It was introduced into Great Britain in 1736.
The much smaller Carolina hemlock (T. caroliniana), some times 7o ft. high, a beautiful but somewhat local tree of the southern Alleghenies from Virginia to Georgia, is extensively planted for ornament. The mountain hemlock (T. Mertensiana), also a small tree, 20 to 90 ft. high, with densely crowded leaves spreading around the branchlets, occurs on high mountains from south-eastern Alaska to Montana and California. Its soft light wood is of but little commercial value. The tree is sparingly grown as an ornamental.
The western hemlock (T. heterophylla), called also hemlock fir and Prince Albert's fir, a valuable timber tree, often 200 ft. high, with a trunk 6 to 1 o f t. in diameter, grows from south eastern Alaska to northern Montana and central California, chiefly near the coast. In quality the wood of the western hemlock is greatly superior to that of all other hemlocks, comparing favour ably with that of pine or spruce. In 1925 the total production of hemlock lumber in the United States was 2,139,631,00o bd. ft., of which 1, 2 28,986,00o bd. ft. was western hemlock, cut in the States of Washington and Oregon, the remainder, except for small quantities of Carolina and mountain hemlock, being eastern hemlock. The cut of western hemlock in the State of Washington was 5 1 % of all the hemlock lumber produced in the United States.
Two Japanese species are cultivated as ornamental trees, namely, Siebold's hemlock (T. Sieboldii), which sometimes grows ft. high, with glossy branches and long-stalked cones, and the Japanese hemlock (T. diversifolia), sometimes attaining a height of 8o ft., with downy branchlets and short-stalked cones. (See