Trees of the Adirondacks:
Eastern Hemlock (Tsuga canadensis)

Trees of the Adirondacks: Eastern Hemlock needles are 1/2 inch in length and flat. Eastern Hemlock on the Barnum Brook Trail (28 July 2012)

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The Eastern Hemlock (Tsuga canadensis) is a medium-sized evergreen tree that flourishes in moist soil in the Adirondacks. This tree is also known as the Canada Hemlock or Hemlock Spruce. It is a member of the pine family. It is the only hemlock native to the Adirondack Mountains. The common name "hemlock" was given because the crushed foliage smells a little like that of the poisonous herb hemlock, which is native to Europe. The Eastern Hemlock is a slow-growing, long-lived tree which may take 250 to 300 years to reach maturity.

The Eastern Hemlock is under severe pressure from the Hemlock Woolly Adelgid, an insect pest native to Asia and accidentally introduced to the US. This pest, which leads to decline and mortality within four to ten years, has thrived along the East coast, damaging hemlock forests from Maine to Georgia. Infestations of this pest have been found in 25 counties of New York State, especially in the Hudson Valley and the Finger Lakes. The insect has not yet spread to the Adirondacks, in part because the main barrier to spread is cold temperatures. There is concern that climate change may help accelerate the spread of the insect, leading to extensive loss of hemlock forests, which would in turn have far-reaching effects on the wildlife species that thrive in the microclimates created by this tree.

Identification of the Eastern Hemlock: The Eastern Hemlock has a loose, irregular, feathery silhouette, with fine, lacy twigs whose tips tend to droop gracefully. This tree has short, flat, blunt, flexible needles, about 1/2 inch long. The needles are rounded at the tip, dark green above and pale silvery below. The needles have rows of tiny teeth on the margins and appear to grow in flat sprays on the lower limbs of trees. The cones of the Eastern Hemlock are very small (about 3/4 inch long) and hang down from the end of the twig. They persist after shedding their seeds in the fall.

Eastern Hemlock bark is thick and rigid. The root system of this species is shallow, making the tree vulnerable to ground fires, drought, and wind. The tree begins to flower at about age fifteen. Male flowers, which appear from April to early June, depending on the locality, are yellow.

Keys to identifying the Eastern Hemlock and differentiating it from other coniferous trees include its needles, bark, and habitat.

• Eastern Hemlock trees are easily distinguished from Eastern White Pine, since the latter tree features much longer needles in bundles, while the needles of the Eastern Hemlock grow individually on the twig.
• Eastern Hemlock needles can also be easily differentiated from those of the Red Spruce, which are sharp-pointed and prickly, growing all around the twig. Eastern Hemlock needles are also arranged spirally, but appear to occupy a single horizontal plane. Moreover, Red Spruce needles are four sided, in contrast to the flat needles of the Eastern Hemlock. Finally, the cones of Red Spruce are much larger than those of the Eastern Hemlock.
• The arrangement of Eastern Hemlock needles also contrasts with that of Tamaracks. Tamarack needles are relatively short, like those of the Eastern Hemlock, but are produced in clusters of ten to twenty, as opposed to the single needles of the Eastern Hemlock.
• Eastern Hemlock is also easy to distinguish from Black Spruce, since the latter species thrives in bogs, where Balsam Fir does not grow.

Differentiating Eastern Hemlock from Balsam Fir is somewhat trickier.

• Balsam Fir needles, like those of the Eastern Hemlock, are flat and white-lined below. In both cases, the needles appear to occupy a single horizontal plane. However, the needles of the Eastern Hemlock are attached to the twig by tiny slender stalks, in contrast to those of the Balsam Fir, which are not stalked.
• The cones of these two species are very different. Those of the Eastern Hemlock are much smaller and pendant, while those of the Balsam Fir are upright.
• The growth habits of the two species are different. The Balsam Fir is conical, with ascending branches, while the Eastern Hemlock has a loose, feathery silhouette. The topmost shoot of hemlocks tend to droop, in contrast to the conical shape of firs and spruces.
• Eastern Hemlock bark lacks the resin blisters characteristic of the bark of young Balsam Fir trees.

Uses of the Eastern Hemlock: The Eastern Hemlock was used by many native American tribes to treat a variety of ailments, including rheumatism, arthritis, colds, coughs, fever, skin conditions, stiff joints, soreness, and scurvy. Native Americans also used the bark to make dyes and the cambium as the base for breads and soups or mixed it with dried fruit and animal fat for pemmican. Natives and white settlers also made tea from hemlock leaves, which have a high vitamin C content. The plant is still sometimes used in modern herbalism, where it is valued for its astringent and antiseptic properties.

At present, the Eastern Hemlock has more limited commercial uses than some other conifers in the region. The characteristics of hemlock wood limit its use to relatively low-grade products, such as structural lumber, pulpwood, and pallets. Although the bark was once a commercial source of tannin, used in the production of leather, synthetic products are now used in leather production. Hemlock bark is still in demand today, but for landscaping mulch. The Eastern Hemlock makes a poor Christmas tree, since its needles fall upon drying. Its value as firewood is limited by the fact that the wood throws sparks. One use that the Eastern hemlock has retained is as an ornamental. The tree can be used as a specimen, screen, or group planting, and can be sheared over time into a formal evergreen hedge,

Wildlife Value of the Eastern Hemlock: Eastern Hemlock provides valuable wildlife food and winter shelter. Many species of wildlife benefit from the excellent habitat that a dense stand of hemlock provides. The dense, low branches of young trees provide winter cover for Ruffed Grouse, Wild Turkey, and other wildlife. For example, White-tailed Deer, which have trouble navigating in snow above twenty inches in depth, may yard up in hemlock groves during periods of heavy snow cover. They may also consume the foliage and twigs of hemlock as high as they can reach. Hemlock bark and twigs also provide winter nutrition for porcupines, and the seeds provide food for Red Squirrels, mice, voles and other rodents.

Eastern Hemlocks are also important in creating a habitat for birds. This species is sometimes chosen as a nest site by Yellow-rumped Warblers. White-winged Crossbills feed on the small, winged seeds from the cones, as do Black-capped Chickadees, Dark-eyed Juncos, Red Crossbills, American Goldfinch, Evening Grosbeaks, and Pine Siskins. The Eastern Hemlock is a common tree species in the breeding habitat of a variety of birds, including:

Blackburnian Warbler	Wood Thrush
Northern Parula	Black-throated Green Warbler
White-throated Sparrow	Golden-crowned Kinglet
Red Crossbill	Red-breasted Nuthatch

Distribution of the Eastern Hemlock: This species  is found in the northeastern part of the US, commonly associated with eastern hardwoods. In Canada, it grows in south-central Ontario, extreme southern Quebec, through New Brunswick, and all of Nova Scotia. Within the United States, Eastern Hemlock occurs throughout New England, the mid-Atlantic states (including most counties in New York State), and the Lake States. The Eastern Hemlock's range extends south in the Appalachian Mountains to northern Georgia and Alabama and west from the mountains into Indiana, western Ohio, and western Kentucky. 

Eastern Hemlock trees are found in boreal forests, mixed conifer/hardwood forests, and northern swamp forests. In the northern hardwood forest, Eastern Hemlock is found on a wide variety of sites, including low rolling hills and glacial ridges.

Eastern Hemlock at the Paul Smiths VIC: Eastern Hemlocks, in contrast to Black Spruce and Tamaracks, do not grow in the middle of bogs or marshes. However, they do like moist areas, so look for them in somewhat swampy areas or near the banks of brooks. They can usually be found in mixed stands, with other conifers and hardwoods that are tolerant of moist soils.

The most convenient place to observe the Eastern Hemlock at the VIC is on the Barnum Brook Trail. This species is one of the eleven tree species marked with signage along this trail. If you take the left hand fork after passing through the gazebo and walk in a clockwise direction, you will find the Eastern Hemlock just before you cross the bridge over Barnum Brook, about half a mile from the gazebo. The tree is located on the left-hand side of the trail, across from the Paper Birch, providing a convenient way of identifying the preferred habitat of these trees. The water of Barnum Brook is a characteristic brown tea color – the result of tannins leaching out of decomposing conifer needles.

References

• United States Department of Agriculture. Forest Service. Silvics of North America. Eastern Hemlock. Retrieved 18 February 2015.
• United States Department of Agriculture. Eastern Hemlock Plant Guide. Retrieved 18 February 2015.
• Lady Bird Johnson Wildflower Center. Native Plant Database. Retrieved 18 February 2015.
• University of Wisconsin. Trees of Wisconsin. Tsuga canadensis. Retrieved 16 February 2015.
• Online Encyclopedia of Life. Tsuga canadensis. Retrieved 18 February 2015.
• University of Wisconsin. Robert W. Freckmann Herbarium. Retrieved 18 February 2015.
• New York Flora Association. New York Flora Atlas. Retrieved 18 February 2015.
• University of Michigan. Native American Ethnobotany. A Database of Foods, Drugs, Dyes and Fibers of Native American Peoples, Derived from Plants. Retrieved 18 February 2015.
• Plants for a Future. Database. Retrieved 18 February 2015.
• The Birds of North America. Magnolia Warbler, Wood Thrush, Blackburnian Warbler, Northern Parula, Black-throated Green Warbler, Canada Warbler, White-throated Sparrow, Golden-crowned Kinglet, Red Crossbill, White-winged Crossbill, Yellow-rumped Warbler, Red-breasted Nuthatch, Subscription Web Site. Retrieved 16 February 2015.
• Trees of the Northern Forest Trail Walk
• New York State Department of Environmental Conservation. Winter Deer Foods. Retrieved 18 February 2015.
• Adirondack Park Invasive Plant Program. Hemlock Woolly Adelgid. Retrieved 18 February 2015.
• US Fish & Wildlife Service. "New York: Invasive Insect Infestations Spread Further North, Threatening Hemlock Forests," Open Spaces, 24 June 2011. Retrieved 18 February 2015.
• Mariko Yamasaki, Richard M. DeGraaf, and John W. Lanier. "Wildlife Habitat Associations in Eastern Hemlock — Birds, Smaller Mammals, and Forest Carnivores," Proceedings: Symposium on Sustainable Management of Hemlock Ecosystems in Eastern North America. USDA Forest Service, 2000. Retrieved 20 February 2015.
• Theodore Howard, Paul Senak, and Claudia Codrescu. "Eastern Hemlock: A Market Perspective," Proceedings: Symposium on Sustainable Management of Hemlock Ecosystems in Eastern North America. USDA Forest Service, 2000. Retrieved 20 February 2015.
• Hugh O. Canham. " Hemlock and Hide: The Tanbark Industry in Old New York," Northern Woodlands, Summer 2011. Retried 20 February 2015.
• Paul Smith’s College VIC. Barnum Brook Tree Game.
• George A. Petrides. A Field Guide to Eastern Trees (Boston: Houghton Mifflin Company, 1998), pp. 40-41, 177-178.
• George A. Petrides. A Field Guide to Trees and Shrubs (Boston: Houghton Mifflin Company, 1958,1972), pp. 4, 21-22, 38-39.
• Gil Nelson, Christopher J. Earle, and Richard Spellenberg. Trees of Eastern North America (Princeton : Princeton University Press), pp. 76-77.
• C. Frank Brockman. Trees of North America (New York: St. Martin's Press), pp. 42-43.
• Keith Rushforth and Charles Hollis. Field Guide to the Trees of North America (Washington, D.C., National Geographic, 2006), p. 72.
• National Audubon Society. Field Guide to North American Trees. Eastern Region. (New York: Alfred A. Knopf, 1980), Plates 20, 483, pp. 299-300.
• Allen J. Coombes. Trees (New York: Dorling Kindersley, Inc., 1992), p. 77.
• John Kricher. A Field Guide to Eastern Forests. North America (Boston: Houghton Mifflin, 1998), pp. 62-67, 72-75, 88-90, 126-127.
• Alexander C. Martin, Herbert S. Zim, and Arnold L. Nelson. A Guide to Wildlife Food Habits (New York: Dover Publications, 1951), pp. 200-201.
• Bruce Kershner, et al. National Wildllife Federation Field Guide to Trees of North America (New York: Sterling Publishing Co., 2008), p. 118-119.
• John Eastman. The Book of Forest and Thicket. Trees, Shrubs, and Wildflowers of Eastern North America (Harrisburg, Pennsylvania, 1992), pp. 101-104.
• David Allen Sibley. The Sibley Guide to Trees (New York: Alfred A. Knopf, 2009), pp.41-42.

Trees of the Adirondack Mountains