When I took these pictures of eastern hemlocks on the campus where I work, I thought the trees were interesting, pretty, and somewhat unusual for this area of mostly pines, oaks, and hickories. I didn’t know they would be removed soon to make way for a parking lot. Eastern hemlocks are in rapid decline nation-wide due to an attack of the hemlock woolly adelgid, but these specimens succumbed to progress.
The eastern hemlock, Tsuga canadensis, is also known as Canadian hemlock. This coniferous evergreen has a range extending from southern Canada and the Great Lakes southward, to the end of the Appalachian Mountain range in northern Georgia and Alabama. It is most often found in 
Georgia on well-drained sites such as those on the lower and on the north or west facing slopes, ridges, and ravines of the north Georgia mountains. This moisture-loving tree is not tolerant of heat or drought, and its thick canopy creates a dense shade that not only reduces the temperature below, but impedes competition by allowing little vegetation to develop around it. Developing hemlocks are shade tolerant, but they grow very slowly in the shade as they await an opening that would allow them to take their place in the canopy. 4,000 miles of mountain streams in Georgia depend on the cooling shade of these trees for survival of trout, and on the trees’ roots to provide soil stabilization for the streams. Many aquatic and forest species 
depend on this tree to survive.
Eastern hemlock trees appear pyramidal when young. They have a slender, flexible and pointed top shoot that tends to weep over. Older trees become more conical, with an irregular rounded crown. Branches are horizontal and gently arching, with leafy horizontal layers. Trees are often found 50 to 70 feet tall and 30 feet wide, but they may grow much larger. The 2010 Atlanta Champion in Fernbank Forest measured 107.4 feet tall. Depending on conditions, growth may range from less than 12 to 24 inches per year. The trunk is usually straight and rarely forked. Bark is cinnamon-brown and scaly on younger trees, and on mature trees 
bark may be 2 to 3 inches thick, gray to brownish, and have deeply fissured ridges and flat plates. Twigs are green to yellow-brown and densely pubescent initially, but become gray-brown and hairless. They occur alternately on the branchlet. Buds are ovid, or egg-shaped, and are 1/8 inch or less in size.
Leaves of the eastern hemlock are evergreen, soft and narrow. They appear as flattened needles. These leaves are most commonly .6 to .8 inch in length, but range from .2 to 1 inch. Largest leaves grow at lower levels. They are attached spirally on the twig by slender peg-like stalks. Those above and below twist so that leaves appear almost lateral and 2-ranked. 
The top surface of new leaves is light shiny green, and that of older leaves is darker. The bottom surface of leaves is whitish, with two broad stomal bands. Leaf margins are very slightly toothed, especially toward the apex. Leaves give the tree a fine texture and persist on the tree up to 3 years, with no autumn change of color.
Trees 20 to 30 years old form strobilli, which are male and female flowers having cone-like structures. Male and female structures are borne on separate branches of the same tree. Female strobilli occur nodding or hanging at the tips of 1-year-old twigs. They are green, oval to elliptic, up to about ¾ inch long, and have fan-shaped scales. Male strobilli 
occur with the leaves along 1-year-old twigs. They are yellowish, nearly round, and ¼ to 1/3-inch-long. Seed cones are ovid, or egg-shaped, and measure up to 1 inch in length and 3/8 to 5/8 inch in width. The ones pictured measured about 1/2 inch long. The scales are ovid to wedge-shaped, and measure up to ½ inch in length and up to 3/8 inch in width. Apex of scales is rounded with minute, irregular teeth along the apex edge. When mature in autumn of the first year, scales open slightly outward and begin releasing seeds in September. The seeds are dispersed by the wind, and require stratification in the cold for approximately 60 days before germinating. Propagation is also possible by 
rooting tip cuttings.
Eastern hemlock provides a natural habitat for many wildlife species. The wood is soft and light with very hard knots, and it is not resistant to rot or insects. It has been used to make crates, boxes, pallets, plywood, general light construction, and pulp. The wood burns poorly, popping and spitting hot embers, and it produces low heat. The bark has been harvested for its high tannin content, to tan leather. Native Americans once used different parts of the tree to treat rheumatism and arthritis, and it has been used as an antiseptic and a cold medicine. Of note, the hemlock tree is unrelated to the poison 
hemlock plant and is not poison. Native Americans used to peel, dry and grind the inner bark layer to make a flour for bread. The tree’s leaves, rich in vitamin C, may be made into a tea. The tree’s leaves may also be eaten, with the young ones usually preferred. The eastern hemlock has enjoyed popular use as a landscape or specimen tree. It makes a beautiful large specimen tree, or can be pruned to make a low hedge.
A danger to the eastern hemlock is the hemlock wooly adelgid, which was accidentally introduced onto the west coast of North America in the 1920’s from Japan. This insect now infects about half the tree’s range from Georgia to New England. Trees in 
many areas have all been killed. Infected trees have a white, waxy and wooly filament protecting the insect’s eggs at the base of needles, with the insect too small to be seen with the unaided eye. The insect sucks the sap from needles, causing them to brown and fall off. Eventually, the tree dies. The insect is spread by wind, birds and animals. Control measures that are being tested and developed include importing, breeding, and releasing 3 known natural beetle predators of the insect. Very cold weather has been observed to kill back the insect, but this helps only under certain conditions. The recent warming of seasons also prevent this from being very helpful. Systemic insecticides are effective and available to treat individual infested trees, but they would not be effective to treat a forest. It is hoped a solution is found to this problem, before all our eastern hemlocks are gone.
We have lost important natural resources to Dutch elm disease, chestnut blight, Southern pine beetle, and now the hemlock wooly adelgid. The eastern hemlock occupies an important place in our eco system, and it is a beautiful tree. We should do all we can to protect this beautiful and important natural resource. I can write an article on a tree I saw that now exists only in pictures, but could Pennsylvania keep its state tree in that way?
