Eastern Hemlock, True to Appalachia
The Eastern Hemlock (Tsuga canadensis) has a quiet resilience like none other. These gentle giants take up residence in sheltered cove forests of the Appalachias. This is my personal all-time favorite tree—read on to see why!
The Eastern Hemlock (Tsuga canadensis) is an elegant plant with wide, reaching branches and a sweeping conical form. The tree is a woody, needled conifer in the Pine Family (Pinaceae). Not a pine, however, this tree has distinct flat needles.
The conifer is native to the eastern United States and Canada—our home in Southern Appalachia marks the southernmost border of this tree’s range. Across our region, Eastern Hemlocks thrive in the fertile understory of cove forests. These small, shaded valleys are characteristic of cool temperatures and humid, damp conditions.
These trees thrive in dappled and deep shade and grow slowly to heights of 40 to 70 feet. Some can reach over 150 feet tall and live past 800! As a native species, the tree attracts moths, small mammals, and songbirds.
Ecologically, the Eastern Hemlock is a vital life source for its community. Mature trees represent keystone species, meaning they play a critical role in the health of their ecosystem. Sometimes called the “redwoods of the east”, these are some of the roles they fill in their communities:
Air Purification: Their root systems and large branches store carbon and filter air and water.
Temperature Regulation: The shade of a hemlock is beneficial for many terrestrial and aquatic animals. In riparian zones, the tree’s canopy maintains cool, stable water temperatures that are crucial for amphibians and fish (like the brook trout).
Wildlife Habitat: As an evergreen, the tree provides year-round coverage and shelter for wintering wildlife.
Food Source: Small mammals and Red Crossbills eat the Eastern Hemlock’s seeds. White-tailed deer seek the foliage in winter when food is scarce, and Ruffled Grouse feed on the tree’s buds.
In ethnobotany, the Eastern Hemlock has been sought after by humans for many years. The leaves can be brewed into a nutritious tea that’s high in vitamin C and antioxidants! The cambium (growing layer of the trunk) was historically used by Indigenous communities as a base for breads and soups and mixed with dried fruit and animal fat for pemmican. The bark was also once used as a tannin in leather production.
Eggs sacs of the Hemlock Wooly Adelgid (HWA) on an Eastern Hemlock
Unfortunately, this species has become victim to the Hemlock Wooly Adelgid (HWA). This aphid-like insect feeds on the sap of new twigs and branches during its crawler stage. Once the insect reaches maturity, it becomes immobile and lays white wooly clusters of egg sacs. Feeding during the winter and early spring prevent the tree from producing new leaves in the growing season. As the tree loses leaves (and its ability to make sugars), the individual will eventually die.
HWA originates from Japan, where populations are controlled by natural predators and immunity in host trees. Since there are no natural predators or genetic resistance to the insect in our local populations, the Eastern Hemlock has suffered steep declines. In the United States, the invasive species now ranges from Georgia all the way to Maine. Conservationists have developed several methods of management, from insecticides to biological control. However, some of these methods may have effects to the greater ecosystem. As land conservation tactics continue to improve, this will be a continued topic of discussion as we aim to save the species without causing harm in other areas.
In my lifetime, I hope to see thriving Eastern Hemlocks and their ecological communities. Together, let’s save this gentle giant!
Local landscape architect Matt Whitaker of WMWA Landscape Architects shares more about the tree’s habit: Eastern hemlock’s native range historically stretched from New Brunswick to the mountains north Alabama and Georgia with a brang over to the great lakes region. In the south it was confined to mostly the Blue Ridge Mountains and immediate surrounds. An accidentally introduced invasive species called the hemlock woolly adelgid has devastated the species killing entire stands in the wild. If you have a hemlock or want to plant it, you can have an arborist treat it with a systemic insecticide that lasts several years to control the insect. Eastern hemlock grows in deep, well-drained but moist soils in full or part-shade in our region. It is evergreen and has a graceful pyramidal shape that can reach up to 70-feet or higher in good conditions. Its dark green needles make it a rare color in our native landscape . It does best when protected from hot summer sun and wind. It does not tolerate drought. With warming average temperatures, increased frequency and length of drought, and the wooly adelgid, eastern hemlock is not a good tree for most in our area. It is not related to the poison hemlock used to kill Socrates. That is a completely different plant family and demonstrates the problem of common names.
