Pennsylvania State Tree
Eastern Hemlock (common name)
Tsuga canadensis (scientific name)
Eastern hemlock ranges from southeast Canada to the northeastern United States, and south along the Appalachian highlands to Georgia and Alabama. In the Appalachians, hemlock favors protected coves along streams, where it is often accompanied by evergreen rhododendrons. Hemlock is reported to be the most shade-tolerant of any tree species in the United States, and the tree is well suited to dark coves and gorges such as Ricketts Glen, one of Pennsylvania's most scenic state parks. Eastern hemlock, also known as Canada hemlock or hemlock spruce, was designated as Pennsylvania's state tree in 1931.
An introduced insect pest, the Asian hemlock woolly adelgid, reached the United States in 1924. The adelgid has now spread through hemlock groves from New England to Georgia. Infestations rapidly overwhelm and kill the trees. Valuable ancient hemlock stands, such as those along the Limberlost Trail in Shenandoah National Park, have been devastated.
Eastern hemlock is a tall, native, evergreen conifer with short, soft flattened needles. Its cones are less than an inch long, with thin rounded scales.
Height: 60-100 ft (18-31 m)
Diameter: 24-48 in (61-122 cm)
Bark: brown, scaly, thin but thickens with age, fissures deepen with age
Cones: less than 1 in (2.5 in) long, thin rounded scales
Leaves: needles, ½-1 in (1.3-2.5 cm) long
Pennsylvania's state tree may live in excess of 800 years.
Eastern hemlock is generally confined to areas with cool and humid climates, with average January temperatures in the range of 10° to 43°F (-12°-6°C). It occurs in coniferous and mixed-hardwood forests. It is often the only conifer present in mixed forests of medium moisture in the eastern United States.
IMPORTANCE TO LIVESTOCK AND WILDLIFE
Dense stands of eastern hemlock provide excellent wildlife habitat. Cove forests in the southern Appalachian Mountains provide nesting habitat for many species of birds. Large eastern hemlocks can be climbed by small black bear cubs. Large, hollow trees are commonly used as dens by black bears. The tree provides cover to ruffed grouse, wild turkey, fishers, and other wildlife. It provides excellent thermal protection and snowfall cover for moose and white-tailed deer in the winter.
The seeds are eaten by birds and mammals, and in the winter the foliage is browsed by white-tailed deer, moose, and snowshoe hares.
OTHER USES AND VALUES
From 1880 to 1930, eastern hemlock was extensively harvested for its bark, which is a source of tannin.
Eastern hemlock is not a premier lumber source. Hemlock groves do not respond well to cutting, since the seedlings require the shaded, moist habitat of the forest to regenerate. Because of brittleness and abundant knots, Eastern hemlock wood is of low value. It is used for pulp, light framing, sheathing, roofing, subflooring, and boxes and crates. The tree is planted as an ornamental.
Trees begin producing seed when they are 20 to 30 years old. Eastern hemlocks older than 450 years still produce large seed crops. Eastern hemlock regeneration appears to be periodic and is influenced by fire, wind, drought, and grouping conditions. A young, dense group may exclude regeneration for many years. Multiple removal cuttings are the best method for regenerating eastern hemlock.
At its western and southern limits, eastern hemlock is confined to moist, cool valleys and flats, northern and eastern slopes, coves, benches, and ravines. In the northern part of its range, the tree tolerates drier and warmer sites. Favorable eastern hemlock sites are moist to very moist with good drainage. Eastern hemlock grows in a wide variety of acidic soils.
In the United States, eastern hemlock occurs throughout New England, the mid-Atlantic states, and the Lake States, and extends south in the Appalachian Mountains to northern Georgia and Alabama and west from the mountains into Indiana, western Ohio, and western Kentucky. At its northern limit, eastern hemlock ranges along the southern border of eastern Canada.
In the northeastern United States, eastern hemlock grows at elevations ranging from sea level to 2,400 feet (730 m). In the southern Appalachian Mountains, it grows from 2,000 to 5,000 feet (610-1,520 m). In the Allegheny Plateau region of New York, Pennsylvania, and Ohio, it is found at 1,000 to 3,000 feet (300-910 m).
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U.S. Forest Service
U.S. National Arboretum
U.S. Department of Agriculture
Author: World Trade Press