A Colorado Blue Spruce is somewhat forgiving when it comes to being trimmed, but if you don't follow the appropriate guidelines, you could end up with a shaggy tree that looks more like a hedge gone berserk than it does a conifer. Of course, you may prefer a fuzzy look to your blue spruce. While the Colorado Blue Spruce can technically be trimmed at any time of the year, trim in the winter or early spring for the best results.
Remove all dead wood and branches. Cut all dead and dying branches back to within 1 inch of the trunk. You will find a swelling (a node) where the branch attaches to the trunk; make your cut just beyond this node, leaving the node on the tree. Trim large branches by making a 1/2 inch deep cut on the underside of the branch at the point where you want the branch cut. Then cut all the way through the branch, cutting from the top side of the branch, about 3 inches beyond the first underside cut you made. In this way the branch can break off cleanly without tearing the bark as you near the completion of your cut. Once the major part of the branch has broken off, cut off the 3-inch stub where you made your first cut.
Review the looks of your tree and cut off branches (following the directions in Step 1) which do not contribute to the overall look you desire. Remember, cutting the ends of a branch will cause your Colorado Blue Spruce to grow "fuzzy" branch ends where you make your cuts.
Do not top a Colorado Blue Spruce. Trim off approximately every third branch if you wish to slow the growth of your spruce and keep it from getting too tall.
Cut lower branches as per the directions in Step 1 to facilitate walking and mowing under the tree. Cut branches that cross each other, or which are rubbing together.