The Eastern hemlock (Tsuga canadensis), also called Canada hemlock, hemlock spruce, or tanbark, is a component of the climax forest of our region. It is a slow-growing, long-lived tree which unlike many trees grows well in shade. It may take 250 to 300 years to reach maturity and may live for 800 years or more. Because early growth of eastern hemlock is so slow, trees less than 2.5 cm (1 in) in diameter may be as old as 100 years and 5 to 8 cm (2 to 3 in) saplings may be 200 years old. Mature eastern hemlock trees may be 110 ft tall and have trunks diameters of 4 ft. The record age is reported to be 988 years, the largest diameter 213 cm (84 in), and maximum height 49 m (160 ft). Eastern hemlock is the most shade tolerant of all tree species, surviving with as little as 5 percent of full sunlight.

Its lower branches are somewhat drooping, and the dense, rather delicate foliage is deep green above and silvery beneath. The flat, narrow leaves are from one-half to three-fourths of an inch long and less than one-twelfth of an inch wide. The hanging cones are as long as or slightly longer than the leaves.

The German name for the hemlock, Tannenbaum, is familiar to us from the Christmas song O Tannenbaum. The German name literally means "tannin tree;" for the bark of the hemlock is rich in tannin, used in curing leathers.

Here is the original German version of the song, along with a translation by Longfellow:

O Tannenbaum, O Tannenbaum,
Wie treu sind deine Blatter.
Du grunst nicht nur zur Sommerzeit,
Nein, auch im Winter wenn es schneit,
O Tannenbaum, O Tannenbaum,
Wie treu sind deine Blatter.

O hemlock-tree! O hemlock-tree! how faithful are thy branches!
Green not alone in summer time,
But in the winter's frost and rime!
O hemlock-tree! O hemlock-tree! how faithful are thy branches!

By the way, the poison hemlock that Socrates drank was not derived from our tree, but from another plant altogether, an herb related to the wild carrot. The tree's scientific name comes from the Japanese name for the hemlock, tsuga.