Tsuga heterophylla / Western hemlock

Tsuga heterophylla, as described in 1898 by (Rafinesque) Charles Sprague Sargent (1841–1927), in The Silva of North America, 12th edition, is commonly known as Western hemlock. It is the state tree of Washington. The species name describes the species' needles of different lengths, a distinctive trait.

Ethnobotany. Tsuga heterophylla is the most economically important hemlock for timber. It is superior to other hemlocks for building purposes and provides excellent pulpwood for paper production. Large swathes of the Washington and Oregon Coast Ranges, as well as Washington's Olympic peninsula, are managed for Tsuga heterophylla production.

Artwork by Bruce L. Cunningham Forester
Artwork by Bruce L. Cunningham Forester

Description. Western hemlock is an evergreen coniferous species of tree that grows to mature heights of 190 to 240 feet (60 - 75 m) tall; with a trunk up to 9 ft (2.7 m) in diameter, measured at breast height; and a narrowly conical crown.

  • Bark is grayish-brown, scaly, and somewhat fissured.
  • Twigs are yellow-brown and finely pubescent.
  • Foliar buds are ovoid shape, grayish-brown in color, measuring 0.1 to 0.14 inch (2.5 - 3.5 mm) long.
  • Leaves (needles ) measure 0.4 to 0.8 inch (10 - 20 mm) long, mostly appearing two-ranked and flattened. Their upper surface is dark green in color, while the underside is glaucous, featuring two broad, conspicuous stomatal bands.
  • Seed cones are ovoid shaped, measuring 0.6 to 1.0 inch (1.5 - 2.5 cm) long and 0.6 to 1.0 inch (1.5 - 2.5 cm) broad.
natural range of <em>Tsuga heterophylla </em>
natural range of Tsuga heterophylla

Distribution. This species is native to the United States of America, distributed through Alaska, Washington, Oregon, California, Montana, and Idaho. In Canada, it grows naturally in British Columbia and Alberta. Its preferred habitat is in coastal and mid-montane forests at elevations from sea level 6,000 feet (1,830 m). Over much of its range, it is a dominant, climax species.

Hardy to USDA Zone 6 — cold hardiness limit between -10° and 0°F (-23.2° and -17.8°C).

Attribution from: Wikipedia, The Free Encyclopedia

Tsuga heterophylla — a closeup of foliage and seed cones.
Photo by Chris Earle, via conifers.org
Tsuga heterophylla — a closeup of bark detail.
Photo by Chris Earle, via conifers.org
Tsuga heterophylla - Detail showing the broad stomatal bands on the underside of foliage. Photographed November 23, 2014 at the Arnold Arboretum, Boston, Massachusetts.
Photo by John Waskiewicz
Tsuga heterophylla — an old growth hemlock stand on Vancouver Island, B.C., Canada
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — veteran hemlock (older than 250 years) and redcedar trees on Vancouver Island, B.C., Canada
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — western hemlock in the the Whitewater Ski Area, Nelson, B.C., Canada
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — a recently harvested and planted area in a hemlock stand, Vancouver Island, B.C., Canada
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — a thrifty hemlock sapling with its drooping top
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — old growth western hemlock (left) and western redcedar (right) near Whistler, B.C., Canada
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — a mixed (uneven-aged) hemlock stand
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — a mixed (uneven-aged) hemlock stand
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — a mature hemlock stand, 180+ years old
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — 120 to 140 year old stand
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — naturally seeded hemlock along the boundary of a harvest block
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — hemlock seeded in from the surrounding mature stand
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — new hemlock seed cones and male pollen cones in the spring
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — new seed cones and male pollen cones in the spring
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — the non-fragmenting cones in winter, dispersing the last of their seeds
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — close-up of hemlock cones
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — cones and a seed of western hemlock
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — Western hemlock seeds
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla — comparison of needles of western hemlock and Pacific yew
Photo by Blake Willson, courtesy of TreeLib.ca
Tsuga heterophylla forest, Cypress Provincial Park, West Vancouver, British Columbia, Canada.

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