Eastern Hemlock (Tsuga canadensis)
Shade Tolerance = Very Tolerant
Soil Moisture Niche = Moist Acidic Sites
Vertical Preference = Canopy
Evergreen boughs and pine-like bark make this conifer easy to identify. Large hemlocks with high foliage can sometimes be confused with white pine. Look on the ground beneath the tree. Hemlock needles are short, flat and blunt-tipped. White pine needles are long, needle-like and come in bundles of five. At higher elevations, where they occasionally occur together, hemlock and red spruce may be confused. Hemlock needles are short, flat and blunt-tipped. Red spruce needles are round or angle-sided and sharp pointed. Hemlock and Fraser fir rarely coincide, but just in case; Fraser fir twigs are tan colored with globe-shaped resinous terminal buds. Scratch Fraser fir twigs; you will smell Christmas! Hemlock twigs are dark colored without obvious terminal buds.
Eastern hemlock is a tree of poetry and legend, or so Longfellow thought when he wrote of the forest primeval in Evangeline. Huge trunks rising one hundred and fifty feet above a bubbling prong supporting a mantle of evergreen boughs sparkling in summer sunlight, create an impression of wild power and beauty well deserving of poetic expression. A century ago, visitors to these mountains routinely slept on beds of fragrant hemlock boughs, a practice today’s environmentally conscious campers no longer subscribe to. It is also against Park regulations!
The Park harbors at least 3000 acres of virgin hemlock forest. Sadly, the hemlock wooly adelgid is rapidly decimating these magnificent trees.
Hemlock thrives in deep shade and on acidic soils. Though indifferent to soil nutrients, it must not venture far from the water of streams or the ample soil moisture found on cool moist protected slopes.
In low elevation river cove forests it shares the canopy with a variety of trees including American sycamore, the diagnostic tree for this forest type.
In mid-succession (intermediate stage) acid cove-hemlock forests, it shares the canopy with poplar, red maple and black birch. As the acid cove-hemlock forest matures, hemlock assumes exclusive dominance by virtue of its extreme shade tolerance and longevity. Rosebay rhododendron often forms the understory in these forests, giving them what Whittaker called, “a somber aspect unrelieved by the verdant green of the deciduous forest.” Hemlocks can live on in the climax forest for centuries. Trees exceeding 500 years in age have been documented in Eastern North America, including GSMNP.
Hemlock often shares the canopy with a large mix of trees including white basswood, mountain silverbell, yellow poplar, yellow buckeye, white ash and sugar maple in the classic cove hardwood forest of middle elevations, and it follows the streams up into the cool cove forest on the North Carolina side, where it grows more sparingly with yellow birch, yellow buckeye and basswood. On upper slopes around 4500 feet elevation hemlock mingles with red spruce and the northern hardwood forest.
The Park has been renowned for giant hemlocks, but the story is almost too sad to tell. The tallest recorded Eastern Hemlock on earth planet was the Usis hemlock located in the Cataloochee District. At 173.1 feet Usis was the tallest of a select group of hemlocks exceeding 170 feet in height. Usis is dead now and only one of the select group, the Noland Mountain Hemlock, survives as of July, 2009. At 171.5 feet tall and 4 feet 4 inches dbh it is the tallest known living Eastern hemlock. The largest hemlock (by wood volume) ever recorded also lived in the Cataloochee District and is also dead.
Both trees were located along Caldwell Creek in Cataloochee where one of the oldest and most magnificent hemlock forests in existence once flourished. Thanks to Will Blozen and the Eastern Native Tree Society we have documented information on these incredible trees, alive now only in Blozen’s photographs and memory.