The blue spruce and its cousins are evergreens. They provide stately, year-round green in the landscape. Slow-growing spruces seldom need pruning, but when they are damaged in storms, they can use some help to avoid further injury. Pruning will not control damage by disease or insects; these are usually controlled by cultural practice alone. Pruning is an extreme measure with spruces. A few specific techniques must be added to basic pruning practice when pruning a damaged spruce to keep it growing straight and tall.
Remove only what is necessary after a storm or other damage. Hanging broken branches that pose a hazard should be removed. Large, open wounds in tree bark that may provide entry points for disease or insects should be addressed. Wait until late winter to complete any cosmetic pruning.
Trim the ragged edges of open wounds that may tear further. Use a sharp knife, cutting as little into the flesh of the tree as possible. Spruce and other evergreens produce large volumes of sticky sap that will flow to wounds and protect the tree.
Remove damaged branches completely if they are broken beyond green needles. Spruce will not regenerate green needles; branches that are broken or pruned back beyond the green will not re-grow.
Hand prune or lop off branch ends by trimming about ¼ inch above the first undamaged joint, or "bud side," or to an undamaged side branch. Spruce, like many evergreens, grows from the tips of its branches. Pruning tips may encourage more side-branch development, growth that spruces, which are naturally thick, do not need.
Prune the trunk only if the tree's life is at risk. A "topped" spruce will never grow straight. It will grow multiple trunks or "leaders". Even if you remove extra leaders, the tree will be unbalanced because the central leader is gone.