Tsuga heterophylla

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Western hemlock
Tsuga heterophylla near Rainier.jpg
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
(unranked): Gymnosperms
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Pinaceae
Genus: Tsuga
T. heterophylla
Binomial name
Tsuga heterophylla
Tsuga heterophylla range map 1.png
Natural range

Tsuga heterophylla, the western hemlock [2] or western hemlock-spruce, [3] is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonoma County, California. [4] [5] The Latin species name means 'variable leaves'. [6]



Branch with mature seed cones that have released their seeds Western hemlock branch.jpg
Branch with mature seed cones that have released their seeds

Western hemlock is a large evergreen conifer growing to 50–70 metres (165–230 feet) tall, exceptionally 83 m (273 ft), [7] and with a trunk diameter of up to 2.7 m (9 ft). It is the largest species of hemlock, with the next largest (mountain hemlock) reaching a maximum height of 59 m (194 ft). The bark is brown, thin, and furrowed (outwardly appearing similar to that of Douglas-fir). [6] The crown is a very neat broad conic shape in young trees with a strongly drooping lead shoot, becoming cylindrical in older trees, which may have no branches in the lowest 30–40 m (100–130 ft). At all ages, it is readily distinguished by the pendulous branchlet tips. The shoots are very pale buff-brown, almost white, with pale pubescence about 1 millimetre (132 in) long.

The leaves are needle-like, 5–23 mm (3162932 in) long and 1.5–2 mm (116332 in) broad, strongly flattened in cross-section, with a finely serrated margin and a bluntly acute apex. They are mid to dark green above; the underside has two distinctive white bands of stomata with only a narrow green midrib between the bands. They are arranged spirally on the shoots but are twisted at the base to lie in two ranks on either side of the shoot. The cones appear on trees over about 25 years old; [6] they are small, pendulous, slenderly cylindrical, 14–30 mm (9161+316 in) long and 7–8 mm (932516 in) broad when closed, opening to 18–25 mm (23323132 in) broad. They have 15–25 thin, flexible scales 7–13 mm (93212 in) long. The immature cones are green, maturing gray-brown 5–7 months after pollination. They are usually plentiful enough to cover the ground beneath the tree. [6] The abundant seeds are brown, 2–3 mm (33218 in) long, with a slender, pale-brown wing measuring 7–9 mm (9321132 in) long. [4] [5] [6]

Initial growth is slow; one-year-old seedlings are commonly only 3–5 centimetres (1+18–2 in) tall, and two-year-old seedlings 10–20 cm (4–8 in) tall. Once established, saplings in full light may have an average growth rate of 50–120 cm (20–47 in) (rarely 140 cm, 55 in) annually until they are 20–30 m (65–100 ft) tall, and in good conditions still 30–40 cm (12–16 in) annually when 40–50 m (130–165 ft) tall. The tallest specimen, 82.83 m (271 ft 9 in) tall, is in Prairie Creek Redwoods State Park, California (United States). The species is long-lived, especially at higher elevations, [6] with trees over 1,200 years old known. [5]

Habitat and ecology

Tsuga heterophylla is an integral component of Pacific Northwest forests west of the Coast Ranges, where it is a climax species. It is also an important timber tree throughout the region, along with many of its large coniferous associates. [8] The species is closely associated with temperate rainforests, and most of its range is less than 100 kilometres (62 miles) from the Pacific Ocean. Valleys it can be found in usually receive at least 80 centimetres (31 inches) of rain annually. [6] It mostly grows at low altitudes, from sea level to 600 m (2,000 ft). In western Washington, it can be found up to elevations of 1,070 m (3,510 ft). [6] The species can also be found in humid areas of mountains further inland, where western white pine is normally dominant. [6] For example, in the Columbia Mountains in and around southeastern British Columbia and northern Idaho, it grows up to 1,500 m (4,900 ft), particularly on north-facing slopes. [6] In the interior part of its range in Idaho, it can be found up to 1,800 m (5,900 ft). [4] [5]

Western hemlock is a very shade-tolerant tree; among associated species in the Pacific Northwest, it is matched or exceeded in shade tolerance only by Pacific yew and Pacific silver fir. [8] Young plants typically grow up under the canopy of other conifers such as Sitka spruce or Douglas-fir, where they can persist for decades waiting to exploit a gap in the canopy. They eventually replace these conifers, which are relatively shade-intolerant, in climax forest. However, storms and wildfires will create larger openings in the forest where these other species can then regenerate. Its thin bark and shallow roots makes it susceptible to fire. [6] At higher elevations, the species can be found mingling with Tsuga mertensiana (mountain hemlock), seeming to take on some of its characteristics although there is no hard evidence of hybridization. [6]

Western hemlock forms ectomycorrhizal associations with some well-known edible fungi such as chanterelles ( Cantharellus formosus , C. subalbidus , and Craterellus tubaeformis ). [9] [10] It is capable of associating with wood-decay fungi in addition to soil fungi; this enables its seedlings to survive on rotting stumps and logs. [11] Older forests are damaged by rot-causing fungi, dwarf mistletoe, and leaf-consuming insects such as Acleris gloverana and Lambdina fiscellaria . [6]


Young specimen Tsuga heterophylla1.jpg
Young specimen

The bark has long served as a source of tannin for tanning leather. [6]


Western hemlock is cultivated as an ornamental tree in gardens in its native habitats and along the U.S. Pacific Coast, where its best reliability is seen in wetter regions. In relatively dry areas, as at Victoria, British Columbia, it is exacting about soil conditions. It needs a high level of organic matter (well-rotted wood from an old log or stump is best; animal manures may have too much nitrogen and salt), in a moist, acidic soil. It is also cultivated in temperate regions worldwide. It has gained the Royal Horticultural Society's Award of Garden Merit. [12] [13]

It can also be found in large gardens in northwest Europe and southern New Zealand.


When planted on the banks of a river, western hemlock can help reduce erosion. Outside of its natural range, the tree is of importance in forestry.

Until the early 1920s, the tree was largely ignored for use as lumber due to its presumed similarity to the poor-quality eastern hemlock. [6] Since then, it has been greatly utilized for timber (as a softwood) and paper production; [6] it is used for making doors, joinery, and furniture. [14] Its fiber is used to make rayon and various plastics. [6]

It has naturalised in some parts of Great Britain and New Zealand—not so extensively as to be considered an invasive species, but as an introduced one.

T. heterophylla often grows on coarse woody debris such as nurse logs and cut stumps. Tsuga heterophylla forest.jpg
T. heterophylla often grows on coarse woody debris such as nurse logs and cut stumps.

Food and medicine

The edible cambium can be collected by scraping slabs of removed bark. The resulting shavings can be eaten immediately, or can be dried and pressed into bread, as was done by the natives of Southeast Alaska. [15] The inner bark was eaten by some Native American tribes as an emergency food, and the bark was cooked to make medicinal extracts for tuberculosis, rheumatic fever, and hemorrhage. [6] The bark could also be boiled to make dark red dyes to make fishing nets and lines less visible to fish. [6]

Western hemlocks have been submerged to collect herring eggs [6] during the spring spawn in southeast Alaska. The boughs provide an easily collectible surface for the eggs to attach to [6] as well as providing a distinctive taste. This practice originates from traditional gathering methods used by Native Alaskans from southeast Alaska, specifically the Tlingit people.[ citation needed ]

Tender new-growth needles can be chewed directly or made into a bitter tea, rich in vitamin C (similar to some other hemlock and pine species).[ citation needed ]


Western hemlock is the state tree of Washington. [16]

Related Research Articles

Douglas fir Species of tree

The Douglas fir is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three varieties: coast Douglas-fir, Rocky Mountain Douglas-fir and Mexican Douglas-fir.

<i>Tsuga</i> Genus of conifers

Tsuga is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage to that of the unrelated plant poison hemlock. Unlike the latter, Tsuga species are not poisonous.

<i>Araucaria heterophylla</i> Species of conifer in the family Araucariaceae

Araucaria heterophylla is a species of conifer. As its vernacular name Norfolk Island pine implies, the tree is endemic to Norfolk Island, an external territory of Australia located in the Pacific Ocean between New Zealand and New Caledonia. It is not a true pine, which belong to the family Pinaceae, but instead is a member of the genus Araucaria, in the family Araucariaceae which also contains the monkey-puzzle tree. Members of Araucaria occur across the South Pacific, especially concentrated in New Caledonia where 13 closely related and similar-appearing species are found. It is sometimes called a star pine, Polynesian pine, triangle tree or living Christmas tree, due to its symmetrical shape as a sapling.

<i>Alnus rubra</i> Species of tree

Alnus rubra, the red alder, is a deciduous broadleaf tree native to western North America.

<i>Thuja plicata</i> Species of conifer in the family Cupressaceae

Thuja plicata is an evergreen coniferous tree in the cypress family Cupressaceae, native to western North America. Its common name is western redcedar, and it is also called Pacific redcedar, giant arborvitae, western arborvitae, just cedar, giant cedar, or shinglewood. It is not a true cedar of the genus Cedrus.

<i>Picea sitchensis</i> Species of large coniferous tree

Picea sitchensis, the Sitka spruce, is a large, coniferous, evergreen tree growing to almost 100 meters (330 ft) tall, with a trunk diameter at breast height that can exceed 5 m (16 ft). It is by far the largest species of spruce and the fifth-largest conifer in the world, and the third-tallest conifer species. The Sitka spruce is one of the few species documented to exceed 90 m (300 ft) in height. Its name is derived from the community of Sitka in southeast Alaska, where it is prevalent. Its range hugs the western coast of Canada and the US, continuing south into northernmost California.

<i>Abies grandis</i> Species of conifer tree

Abies grandis is a fir native to the Pacific Northwest and Northern California of North America, occurring at altitudes of sea level to 1,700 metres (5,600 ft). It is a major constituent of the Grand Fir/Douglas Fir Ecoregion of the Cascade Range.

<i>Abies concolor</i> Conifer (pine tree) found in North America

Abies concolor, the white fir, is a coniferous tree in the pine family Pinaceae. This tree is native to the mountains of western North America, including the Cascade Range and southern Rocky Mountains, and into the isolated mountain ranges of southern Arizona, New Mexico, and Northern Mexico. It naturally occurs at elevations between 900–3,400 metres (3,000–11,200 ft).

<i>Acer macrophyllum</i> Species of maple

Acer macrophyllum, the bigleaf maple or Oregon maple, is a large deciduous tree in the genus Acer.

<i>Tsuga canadensis</i> Species of conifer

Tsuga canadensis, also known as eastern hemlock, eastern hemlock-spruce, or Canadian hemlock, and in the French-speaking regions of Canada as pruche du Canada, is a coniferous tree native to eastern North America. It is the state tree of Pennsylvania. Eastern hemlocks are widespread throughout much of the Great Lakes region, the Appalachian Mountains, the Northeastern United States, and Maritime Canada. They have been introduced in the United Kingdom and mainland Europe, where they are used as ornamental trees.

<i>Tsuga mertensiana</i> Species of tree found in western North America

Tsuga mertensiana, known as mountain hemlock, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Tulare County, California. Mertensiana refers to Karl Heinrich Mertens (1796–1830), a German botanist who collected the first specimens as a member of a Russian expedition in 1826–1829.

<i>Picea glauca</i> Species of conifer

Picea glauca, the white spruce, is a species of spruce native to the northern temperate and boreal forests in North America. Picea glauca is native from central Alaska all through the east, across southern/central Canada to the Avalon Peninsula in Newfoundland, and south to Montana, Minnesota, Wisconsin, Michigan, Vermont, New Hampshire, New York and Maine; there is also an isolated population in the Black Hills of South Dakota and Wyoming. It is also known as Canadian spruce, skunk spruce, cat spruce, Black Hills spruce, western white spruce, Alberta white spruce, and Porsild spruce.

<i>Tsuga caroliniana</i> Species of conifer

Tsuga caroliniana, the Carolina hemlock, is a species of Tsuga, native to the Appalachian Mountains in southwest Virginia, western North Carolina, extreme northeast Georgia, northwest South Carolina, and eastern Tennessee. Its habitat is on rocky mountain slopes at elevations of 700–1,200 m (2,300–3,900 ft). The optimal growing condition is a partly shady area with moist but well-drained soil in a cool climate.

<i>Abies amabilis</i> Species of conifer

Abies amabilis, commonly known as the Pacific silver fir, is a fir native to the Pacific Northwest of North America, occurring in the Pacific Coast Ranges and the Cascade Range. It is also commonly referred to as the white fir, red fir, lovely fir, Amabilis fir, Cascades fir, or silver fir. The species name is Latin for 'lovely'.

Northern Pacific coastal forests Temperate coniferous forests ecoregion of Alaska, United States

The Northern Pacific coastal forests are temperate coniferous forest ecoregion of the Pacific coast of North America. It occupies a narrow coastal zone of Alaska, between the Pacific Ocean and the northernmost Pacific Coast Ranges, covering an area of 23,300 square miles, extending from the Alexander Archipelago in southeast Alaska along the Gulf of Alaska to the western Kenai Peninsula and eastern Kodiak Island. The Pacific Coastal Mountain icefields and tundra ecoregion lies inland, at higher elevations in the Coast Mountains. The ecoregion receives high rainfall, which varies considerably based on exposure and elevation. It contains a quarter of the world's remaining temperate rain forest.

Management of Pacific Northwest riparian forests is necessary because many of these forests have been dramatically changed from their original makeup. The primary interest in riparian forest and aquatic ecosystems under the Northwest Forest Plan (NWFP) is the need to restore stream habitat for fish populations, particularly anadromous salmonids. Some of these forests have been grazed by cattle or other livestock. The heavy hooves of these animals compact the soil. This compaction does not allow the water to be absorbed into the ground, so the water runs off into the stream carrying topsoil along the way.

<i>Craterellus tubaeformis</i>

Craterellus tubaeformis is an edible fungus, also known as yellowfoot, winter mushroom, or funnel chanterelle. It is mycorrhizal, forming symbiotic associations with plants, making it very challenging to cultivate. It is smaller than the golden chanterelle and has a dark brown cap with paler gills and a hollow yellow stem. C. tubaeformis tastes stronger but less fruity than the golden chanterelle. It has a very distinctive smokey, peppery taste when raw. It grows in temperate and cold parts of Northern America and Europe, including Scandinavia, Finland, Russia, and the British Isles, as well as in the Himalayas in Asia, including Assam, in the central parts of the Indian subcontinent, and in Thailand.

Ecology of the North Cascades Ecosystems of the Cascade mountain range in northern Washington state and southern British Columbia

The Ecology of the North Cascades is heavily influenced by the high elevation and rain shadow effects of the mountain range. The North Cascades is a section of the Cascade Range from the South Fork of the Snoqualmie River in Washington, United States, to the confluence of the Thompson and Fraser Rivers in British Columbia, Canada, where the range is officially called the Cascade Mountains but is usually referred to as the Canadian Cascades. The North Cascades Ecoregion is a Level III ecoregion in the Commission for Environmental Cooperation's classification system.

<i>Rhododendron menziesii</i>

Rhododendron menziesii, also classified as Menziesia ferruginea, is a species of flowering plant in the heath family Ericaceae, known by several common names, including rusty menziesia, false huckleberry, fool's huckleberry and mock azalea.

<i>Pseudotsuga menziesii <span style="font-style:normal;">var.</span> menziesii</i> Variety of conifer

Pseudotsuga menziesii var. menziesii, also known as Coast Douglas-fir, Pacific Douglas-fir, Oregon pine, or Douglas spruce, is an evergreen conifer native to western North America from west-central British Columbia, Canada southward to central California, United States. In Oregon and Washington its range is continuous from the Cascades crest west to the Pacific Coast Ranges and Pacific Ocean. In California, it is found in the Klamath and California Coast Ranges as far south as the Santa Lucia Mountains with a small stand as far south as the Purisima Hills, Santa Barbara County. In the Sierra Nevada it ranges as far south as the Yosemite region. It occurs from near sea level along the coast to 1,800 metres (5,900 ft) in the California Mountains. Further inland, coast Douglas-fir is replaced by Rocky Mountain or interior Douglas-fir. Interior Douglas-fir intergrades with coast Douglas-fir in the Cascades of northern Washington and southern British Columbia.


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