Eastern Hemlock & Woolly Adelgid

The Eastern Hemlock, Tsuga canadensis, is one of several important forest species facing new threats. Look at the information below and examine the trees that we have in our forest. Are our Eastern Hemlocks being effected by the Woolly Adelgid? Inspect them as you walk the trail.

Eastern Hemlock

Climate: The Eastern hemlock grows in cool humid climates in the North Eastern United States. The trees grow best in areas of high rain falls with 29 to 50 inches. These hemlocks grow biggest and tallest in the Appalachian mountain chain.


Leaf and Cones and Bark: The leaves are typically 0.5 to 1 inch in length. They are flattened and are typically parallel with the leaf on the opposing side with no leaf sprouting on the top or bottom of the twig. The leaves are dull and rounded on the end. The bottom of the leaf is split, while the top is a shiny green to yellow-green in color. The seed cones are oval in shape and typically measure 0.5 to 1 inch in length. The bark is brownish, scaly, and deeply fissured, especially with age. The twigs are a yellow-brown in color, and are densely pubescent.

Below is a great image of the underside of a hemlock twig showing the white stripes on the underside of each needle which is singly born on the stem.

Interesting Info: The oldest recorded tree was at least 554 years old! The lumber is used for general construction and crates. Because of its unusual power of holding spikes, it is also used for railroad ties. Untreated, the wood is not durable if exposed to the elements. The tree generally reaches heights of about 100 feet, but exceptional trees have been recorded up to 173 feet. The trunk is usually straight but very rarely it can become forked. The tallest now surviving, the "Noland Mountain tree", is 170 ft tall. One tree has been measured in the Great Smoky Mountains National Park to 173 ft tall, though sadly, this tree is now dead from hemlock woolly adelgid.

Woolly Adelgid is a species of beetle that is from South East Asia and sucks the sap from hemlocks. In eastern North America, it is a destructive pest that gravely threatens the eastern hemlock and the Carolina hemlock. The pest has now been established in eleven eastern states from Georgia to Massachusetts, causing widespread mortality of hemlock trees. The presence of Woolly Adelgid can be identified by its egg sacs, which resemble small tufts of cotton clinging to the underside of hemlock branches. Hemlocks stricken by Woolly Adelgid frequently become grayish-green rather than the dark green of healthy hemlocks. The current leading biological control method of hemlock woolly adelgid is Pseudoscymnus tsugae. P. tsugae is a black lady beetle that is host specific, feeding only on hemlock woolly adelgid, balsam woolly adelgid, and pine bark adelgid. This beetle was discovered feeding on hemlock woolly adelgid in its natural homeland of Japan in 1992. Since 1995 the DCNR's Bureau of Forestry has released more than 100,000 adult beetles in infested hemlock forests throughout Connecticut, New Jersey and Virginia.