Tsuga heterophylla

Tsuga heterophylla subsp. var.	Western hemlock
	Habit: tree Height: ⇕ to Width: ⇔ to 60ft120ft 20ft30ft Height: ⇕ 60 ft to 120 ft Width: ⇔ 20 ft to 30 ft Lifespan: ⌛ perennial Origin: ✈ Poisonous: ☠ Bloom: ❀	Exposure: ☼ sun Water: ◍ Features: ✓ edible Hidden fields, interally pass variables to right place Minimum Temp: ☃ °Fwarning.png"°F" is not a number. USDA Zones: 6 to 10 Sunset Zones: Flower features: ❀
	Pinaceae > Tsuga heterophylla var. ,

Tsuga heterophylla (Western 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 Sonoma County, California.

It is a large evergreen coniferous tree growing to 50-70 m tall, exceptionally 78 m, and with a trunk diameter of up to 2.7 m. It is the largest species of hemlock, with the next largest (Mountain Hemlock T. mertensiana) reaching a maximum of 59 m. The bark is brown, thin and furrowed. The crown is a very neat broad conic shape in young trees with a strongly drooping lead shoot, becoming cylindric in older trees; old trees may have no branches in the lowest 30-40 m. 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 mm long. The leaves are needle-like, 5-23 mm long and 1.5–2 mm 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 are small, pendulous, slender cylindrical, 14-30 mm long and 7-8 mm broad when closed, opening to 18-25 mm broad. They have 15–25 thin, flexible scales 7-13 mm long. The immature cones are green, maturing gray-brown 5–7 months after pollination. The seeds are brown, 2-3 mm long, with a slender, 7-9 mm long pale brown wing.

It is closely associated with temperate rain forests, and most of its range is less than 100 km from the Pacific Ocean. There is however an inland population in the Rocky Mountains in southeast British Columbia, northern Idaho and western Montana. It mostly grows at low altitudes, from sea level to 600 m, but up to 1800 m in the interior part of its range in Idaho.

Initial growth is slow; one year old seedlings are commonly only 3-5 cm tall, and two year old seedlings 10-20 cm tall. Once established, saplings in full light may have an average growth rate of 50-120 cm (rarely 140 cm) annually until they are 20-30 m tall, and in good conditions still 30-40 cm annually when 40-50 m tall.

It is a very shade-tolerant tree, with young plants typically growing up under the canopy of other conifers such as Sitka Spruce and Douglas-fir, then eventually replacing them in climax forest as those species cannot grow in the dense shade cast by Western Hemlocks. However, storms and (rarely) wildfires will create larger openings in the forest where these other species can then regenerate. The tallest specimen, 78.9 m tall, is in Prairie Creek Redwoods State Park, California (USA). It is long-lived, with trees over 1200 years old known.

Standard Cyclopedia of Horticulture

Tsuga heterophylla, Sarg. (T. Albertiana, Senecl. T. Mertensiana, Carr.). Tree, attaining 200 ft., with short slender, usually pendulous branches forming a rather narrow pyramidal head in older, but rather broad in young trees: young branchlets pale yellowish brown, pubescent: lvs. linear, obtuse or acutish, distinctly grooved and dark green above, with 2 white lines below, 1/2 – 3/4 in. long: cones oblong-ovoid, sessile, 3/4 - 1 in. long; scales oval, slightly puberulous outside. Alaska to Calif., west to Mont. Var. argenteo-variegata, Schneid. Tips of the young branchlets white. CH The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.

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References

• Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963

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