The western hemlock, also known as Pacific hemlock or lowland hemlock, is a tall and impressive evergreen conifer that grows predominantly along the West Coast of North America. A valuable tree commercially, western hemlock is also important as a resource for wildlife. Western hemlock is also the official state tree of Washington.
Western hemlock ranges from Alaska to California and as far east as Montana. It is much more common west of the Cascade mountains. The tree grows well in hardiness zones 5 through 7 and is marginally successful in zones 3 and 4.
The leaves are flat needles with a groove down the center. They are glossy and yellowish-green in appearance on the upper surface and whitish over most of the lower surface. The needles vary between 1/4 and 3/4 inch in length and alternate along a 4- to 6-inch stem. The bark is dark brown to reddish brown in color. As the tree ages, the bark becomes thick and furrowed. The flowers of the tree form separate male and female cones. The male cones are tiny and insignificant. The female cones are between 1/8 and 1/4 inch in length. Female cones, once mature, are hard, brown and made up of overlapping scales that protect the seeds.
The tree grows from a single, straight, upright leader trunk that can reach more than 150 feet in height. The majority of the foliage usually appears on the upper third of the tree and is roughly pyramidal in form. The branches of the tree radiate from the central trunk and tend to droop. The canopy of the tree is relatively open and finely textured.
Western hemlock trees prefer acidic soils that remain moist or even wet for a period of time, but that drain well. The tree prefers full sun, although it is very tolerant of partial or even full shade and can frequently be found growing under the forest canopy. Western hemlock should be planted in the cooler areas of the landscape as it does not adapt well to the heat of the summer. The tree can be sensitive to salt and air pollution and is prone to high wind damage. Propagation of western hemlock is primarily by seed.
Western hemlock is an important environmental resource. It is often used by wildlife, such as deer and elk, for forage. Rabbits, beavers and other herbivorous animals frequently consume the stems of saplings. Birds, such as woodpeckers and owls, that nest in cavities in trees frequently use western hemlock.
Commercially, the wood of western hemlock is used for construction lumber, posts, railroad ties and pulpwood. The wood is also a major source of alpha cellulose fiber, a common material used in the manufacture of cellophane, rayon and plastics.