This month we present the Canadian Hemlock, Tsuga canadensis: a medium to large tree native to the eastern U.S. from Canada to Georgia.
In the east there are two species, the Canadian (or Eastern) Hemlock and the Carolina Hemlock, which is limited to a small area of the southern Appalachians. In addition, there are two western U.S. species and four to six species native to eastern Asia. The botanical name of hemlocks, Tsuga, is derived from the town of the same name in Japan. The common name results from a perceived similarity to the odor of crushed leaves of poison hemlock—however, hemlock trees are not poisonous.
In our area they may grow to 70 feet or more, while in the Great Smokey Mountains specimens up to nearly 175 feet have been measured. Hemlocks are found primarily on rocky ridges, ravines and hillsides. They are very long lived: in Cook Forest, Pa. there are trees more than 550 years old!
The two eastern U.S. species are both under serious threat by the woolly adelgid, a small white sap-sucking insect related to aphids. It was introduced accidentally from eastern Asia, where it is only a minor pest. In the south of its range the danger seems more severe; in the Great Smokey Mountains thousands of acres of hemlocks have been killed.
The Canadian Hemlock is the state tree of Pennsylvania. At Kendal we have some fine specimens near Parking Lot 3A that seem resistant to the adelgid (see No. 56 on the South Loop adopted by Judy Czeiner). Let us hope that hemlocks do not go the way of elms and chestnuts!
The Canadian Hemlock has small needles (leaves) generally up to about 1⁄2 inch long. The small scaled cones are pendant and about 5/8 to 1 inch long. A number of small mammals, deer and birds eat the twigs and seeds.
Martin Wells and Judy Czeiner, Photographer