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Tsuga heterophylla
Tsuga heterophylla, the western hemlock or western hemlock-spruce, is a species of hemlock. It typically grows to 70 metres (230 feet) tall and is long-lived at high elevations. Native to the northwest coast of North America, it is a source of timber, tannin, and edible cambium.
Western hemlock is a large evergreen conifer growing to 50–70 metres (160–230 feet) tall, exceptionally 83 m (272 ft), and with a trunk diameter of up to 2.7 m (9 ft). It is the largest species of hemlock, with the next largest (T. mertensiana or mountain hemlock) reaching a maximum height of 59 m (194 ft). Western hemlock's bark is brown, thin, and furrowed (outwardly appearing similar to that of Douglas-fir). The crown is a very neat broad conic shape in young trees with a strongly drooping lead shoot, and becomes 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 (1⁄32 in) long.
The leaves are needle-like, 5–25 mm (3⁄16–1 in) long and 1.5–2 mm (1⁄16–3⁄32 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; they are small, pendulous, slenderly cylindrical, 14–30 mm (1⁄2–1+1⁄8 in) long and 7–8 mm (1⁄4–5⁄16 in) broad when closed, opening to 18–25 mm (3⁄4–1 in) broad. They have 15–25 thin, flexible scales 7–13 mm (1⁄4–1⁄2 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. The abundant seeds are brown, 2–3 mm (1⁄16–1⁄8 in) long, with a slender, pale-brown wing measuring 7–9 mm (1⁄4–3⁄8 in) long.
Initial growth is slow; one-year-old seedlings are commonly only 3–5 centimetres (1+1⁄8–2 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. The species is long-lived, especially at higher elevations, with trees over 1,200 years old known.
The Latin heterophylla in the species name means 'variable leaved'.
Tsuga heterophylla is native to the northwest coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonoma County, California.
The species 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. 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 cm (31 in) of rain annually. 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). The species can also be found in humid areas of mountains further inland, where western white pine is normally dominant. 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. In the interior part of its range in Idaho, it can be found up to 1,800 m (5,900 ft).
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.
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Tsuga heterophylla
Tsuga heterophylla, the western hemlock or western hemlock-spruce, is a species of hemlock. It typically grows to 70 metres (230 feet) tall and is long-lived at high elevations. Native to the northwest coast of North America, it is a source of timber, tannin, and edible cambium.
Western hemlock is a large evergreen conifer growing to 50–70 metres (160–230 feet) tall, exceptionally 83 m (272 ft), and with a trunk diameter of up to 2.7 m (9 ft). It is the largest species of hemlock, with the next largest (T. mertensiana or mountain hemlock) reaching a maximum height of 59 m (194 ft). Western hemlock's bark is brown, thin, and furrowed (outwardly appearing similar to that of Douglas-fir). The crown is a very neat broad conic shape in young trees with a strongly drooping lead shoot, and becomes 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 (1⁄32 in) long.
The leaves are needle-like, 5–25 mm (3⁄16–1 in) long and 1.5–2 mm (1⁄16–3⁄32 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; they are small, pendulous, slenderly cylindrical, 14–30 mm (1⁄2–1+1⁄8 in) long and 7–8 mm (1⁄4–5⁄16 in) broad when closed, opening to 18–25 mm (3⁄4–1 in) broad. They have 15–25 thin, flexible scales 7–13 mm (1⁄4–1⁄2 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. The abundant seeds are brown, 2–3 mm (1⁄16–1⁄8 in) long, with a slender, pale-brown wing measuring 7–9 mm (1⁄4–3⁄8 in) long.
Initial growth is slow; one-year-old seedlings are commonly only 3–5 centimetres (1+1⁄8–2 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. The species is long-lived, especially at higher elevations, with trees over 1,200 years old known.
The Latin heterophylla in the species name means 'variable leaved'.
Tsuga heterophylla is native to the northwest coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonoma County, California.
The species 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. 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 cm (31 in) of rain annually. 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). The species can also be found in humid areas of mountains further inland, where western white pine is normally dominant. 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. In the interior part of its range in Idaho, it can be found up to 1,800 m (5,900 ft).
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.