Eastern hemlock

Eastern hemlock (Tsuga canadensis), also known as Canadian hemlock, Canada hemlock, Hemlock, or Hemlock spruce, is an evergreen conifer tree which is native to southeastern Canada, the northeastern United States, and along the Appalachian mountains, stretching into north Alabama. It is the only hemlock variety native to Alabama.

The hemlock is noted for tolerating more shade than other evergreens and thrives on north-facing slopes, in deep ravines, and along streams, where it finds moist soil. When grouped in stands of hemlock, their dense foliage can create microclimates with very little sunlight reaching the surface of the ground or streams.

The tree grows into an upright pyramidal form with a furrowed reddish-brown trunk, branches extending to the ground. The flattened needles are about 1/2" to 3/4" long, paired, growing in two rows along each sprig. The small seed cones, rarely reaching an inch long, emerge as tight green ovals and mature to open gray-brown cones in mid-October, releasing small seeds to be dispersed by wind. The seeds are vulnerable to drying and germinate best in warm, moist soils. Seedlings are vulnerable to root rot fungi if present.

Hemlocks are slow-growing, and long-lived. In the Southern Appalachian range, 50-foot tall trees with 9-inch diameter trunk may be more than 40 years old. True maturity is thought to require 250–300 years, and several specimens exceeding 800 years have been identified.

Hemlock lumber is a medium-brown colored coarse-grained softwood. Between 1890 and 1910 it was heavily used for railroad ties, pallets, crates and framed buildings. Since then it is mostly used for paper making. The bark is rich in tannins and was formerly used to tan hides. Its historic range has been reduced in the mid-20th century by over-timbering. Seedlings are consumed by rodents in winter, and younger trees are vulnerable to over-browsing by white-tailed deer. Mature trees have some resistance to fire.

More recently, eastern hemlock has been affected by infestation by the hemlock wooly adelgid (HWA), an invasive aphid-like insect. Affected trees are unable to maintain their needles, which turn brown and fall, weakening the tree and making it more vulnerable to other threats, such as the hemlock borer beetle. Infestations usually result in death within 3 to 5 years.

The southernmost stand of eastern hemlock is believed to inhabit Village Creek Canyon below Bayview Dam in western Jefferson County.

The largest eastern hemlock every recorded was 175 feet tall with a trunk diameter of 76 inches. Alabama's "Champion" eastern hemlock, first recognized in 1992, is 120 feet tall with an average diameter of 25 feet and a trunk diameter of 48.4 inches. It is located in the William B. Bankhead National Forest in Winston County.

References

• Godman, R. M. & K. Lancaster (1990) "Hemlock" in Silvics of North America. USDA Forest Service Agriculture Handbook 654, Vol. 1
• Knoepp, J. D., K. J. Elliott, et al. (2007). "Eastern hemlock forests in the southern Appalachians: Vegetation and soil characteristics." Southern Appalachian Man and the Biosphere Conference. Johnson City, Tennessee, No. 43.
• Angel, Josh (2023) "Trees of Alabama: Eastern Hemlock." Alabama's Treasured Forests. Alabama Forestry Commission, Vol. 42, No. 3, p. 32