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| Picea sitchensis – Sitka Spruce |
Picea sitchensis commonly known as Sitka spruce. Its
introduced by David Douglas in 1831 is nowadays the most extensively planted
tree in British forestry. It takes its name from the small seaport of Sitka in
Alaska, but is found as a native southwards from that state to north
California. It is a large growing tree, grow up to 100 m (330 ft), with huge trunk up to 5m (16 ft) in diameter.
The young shoots are light brown to pure white. The buds are
ovoid and yellowish-brown and free of resin. The needles stand out stiffly
around the shoot, and are bluish-green on the upper surface, with a prominent
rib; the lower surface bears two bands of white stomata giving a blue or
silvery appearance. The needles are flattened up to 2 cm long and have sharp
horny points. Each needle stands on a little peg projecting from the twig; when
pulled away, the peg goes with the needle, accompanied by a short strip of
bark. In mass the needles give the tree a faintly blue sheen.
The flowers of both sexes are found on the same tree. The
stalked male catkins are about 2.5 cm long, oval, pendulous or spreading, red
at first but becoming yellow. The female flowers, usually higher up the tree,
are small oval, erect structures, stalk less and crimson-colored; they have
prominent bract which are eventually covered by the developing scales. The
cone, 5-8 cm long and blunt-ended, has papery-textured scales with crinkled
edges, and is light brown becoming whitish or pale yellow. It ripens in the
first year, releasing the seeds early in autumn and then persisting on the tree
for indefinite periods.
The bark is at first greyish-brown and looks smooth (though
rough to the touch), later breaking into greyish-brown round scales, with
somewhat raised edges (in appearance like small shallow saucers), which
gradually flake away. The tree is at first conical in shape, later developing
long lightly drooping branches and a rather thin crown. The base usually
broadens out and is often buttressed. The wood is tough but has no natural
durability out of doors; it is white to pale yellow in color – much used for
box-making, interior joinery and carpentry, shed-building, paper pulp,
chipboard, pit-props, and general purposes.
Foresters appreciate Sitka Spruce as a fine
forest tree for the peaty hills and moors where the rainfall is heavy. It is
more resistant to exposure and possibly more wind-firm than Norway Spruce and
in general faster growing and produces a larger volume of timber. It can exceed
100 feet in thirty years and several trees are known over 150 feet and some
exceed 20 feet in girth. Sitka particularly in drier areas is partially
defoliated annually by the attacks of an aphis Elatobium abietina, making the
tree appear much thinner foliaged than Norway Spruce. High moisture
requirements make it unsuitable for the drier climates and soils of the south
and east of Britain.
