Sitka Spruce
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| Sitka Spruce Conservation status: Secure | ||||||||||||||
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| Missing image Piceasitchensis.jpg Young Sitka Spruce in a forestry plantation in Britain | ||||||||||||||
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The Sitka Spruce (Picea sitchensis) is a large evergreen tree growing to 50-70 m tall, exceptionally to 96 m tall, and with a trunk diameter of up to 5 m. It is by far the largest species of spruce, and the third tallest tree species in the world (after Coast Redwood and Coast Douglas-fir).
| Missing image Sitka_Spruce_forest.jpg Sitka Spruce forest in the Olympic Mountains, Washington |
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| Missing image SS1.jpg Foliage, mature seed cone and (centre) old pollen cone |
It is native to the west coast of North America, with its northwestern limit on Kodiak Island, Alaska, and its southeastern limit just north of San Fransisco, California. It is closely associated with temperate rain forests, and nowhere does its range extend more than 80 km from the Pacific Ocean.
The bark is thin and scaly, flaking off in small circular plates 5-20 cm across. The crown is broad conic in young trees, becoming cylindric in older trees; old trees may have no branches in the lowest 30-40 m. The shoots are very pale buff-brown, almost white, and glabrous (hairless) but with prominent pulvini. The leaves are needle-like, 15-25 mm long, flattened in cross-section, dark glaucous blue-green above with two or three thin lines of stomata, and blue-white below with two dense bands of stomata.
The cones are pendulous, slender cylindrical, 5-11 cm long and 2 cm broad when closed, opening to 3 cm broad. They have thin, flexible scales 15-20 mm long; the bracts just above the scales are the longest of any spruce, occasionally just exserted and visible on the closed cones. They are green or reddish, maturing pale brown 5-7 months after pollination. The seeds are black, 3 mm long, with a slender, 7-9 mm long pale brown wing.
Trees over 90 m tall may be seen in the Pacific Rim National Park on Vancouver Island, British Columbia (the 'Carmanah Giant', at 96 m tall the tallest tree in Canada), and in the Olympic National Park, Washington and Prairie Creek Redwoods State Park, California (USA); two at the last site are just over 96 m tall. It is long-lived, with trees over 700 years old known.
A unique specimen with golden foliage growing on the Queen Charlotte Islands, known as Kiidk'yaas, is sacred to the Haida Native American people.
Outside of its native range, Sitka Spruce is of major importance in forestry for timber and paper production, and as an ornamental tree in large gardens, in northwest Europe and southern New Zealand. Sitka Spruce is also known for its high strength and regular, knot free rings, which make it an important material for homebuilt aircraft. It is particularly valued for its fast growth on poor soils and exposed sites where few other trees can be grown successfully; in ideal conditions young trees may grow 1.5 m per year. It is naturalised in some parts of Britain and New Zealand, though not so extensively as to be considered an invasive weed tree.
External links
- Gymnosperm Database (http://www.botanik.uni-bonn.de/conifers/pi/pic/sitchensis.htm)
- Arboretum de Villardebelle - photos of cones of Picea sitchensis and related spruces (http://www.pinetum.org/cones/PICEAcones.htm)da:Sitka-Gran (Picea sitchensis)