There are between 35 and 40 species of spruce, an evergreen conifer, found throughout the Northern Hemisphere around the world. Native spruce trees prefer climates ranging from wet winters and hot, dry summers to cold, snowy winters and warm, moist to dry summers. The spruce does well in poor soil and is considered a moderately-fast to fast-growing tree.
The spruce can be recognized by its needles that radiate equally in all directions around each branch. The needles grow from a projection on the branch. When the needles fall off, the projections are left and the branch is rough to the touch. The needles are four-sided except for the Sitka and Brewer species, which are are flat. Spruce needles, except for the black spruce, are sharp and rigid. The needles on the black spruce are rigid and blunt.
The cones of the spruce are oblong and thin-skinned when young. They grow downward at the ends of the upper branches of the tree. Spruce cones open and drop their seeds during their first autumn, then generally fall off within a year. The exceptions are the white spruce, which keeps its cones for two years, and the black spruce, which keeps its cones for 30 years. These two exceptions function as fire cones that release seeds when heated. Certain species of spruce are susceptible to a parasite called a spruce gall adelgid that feeds on the tips of the branches and needles.
The branches of the spruce grow from the trunk, from the ground to the crown of the tree. Older branches are located closer to the ground. New branches, called branchlets, are continually being added at the top of the tree. Spruces in the wild routinely lose branches and gaps may develop in the tree. On all spruces except the Brewer, the branches point up. The primary branches on the Brewer spruce grow horizontally while the secondary branches hang downward in a weeping fashion to shed heavy snow.
Trunk and Bark
The trunks of the spruce are generally column-shaped and straight, lending to the trees' overall pyramid shape. The trunk of the Sitka spruce, the largest of the spruces, is fluted with a wider base than other spruce trees. The seedlings of the Sitka spruce will sprout on top of dead trees, called nurse logs. The spruce will burrow through the rotted wood of the nurse log, developing stilt-like roots.
Spruce tree bark ranges in color from smooth gray to purple-gray when young. The bark cracks and fissures with age in all spruces.
Commercial and Natural Uses
All species of the spruce, except for the Brewer spruce, are valued for their timber, which is used for construction. Spruces are also harvested for pulp.
Because it is fast growing, the spruce is used in reforesting projects, as a landscape tree and as a windbreak. Navajo use the branches of the Englemann spruce in sweat lodges and for ceremonial purposes.
In the wild, the spruce provides shelter and food to animals, specifically the spruce grouse, which depends on spruce needles for food.