Evergreens can be trimmed at any time, but doing so in spring before new growth occurs is generally considered the best. Evergreens are trimmed to promote new growth, control their shape, and decrease the risk of disease. With a lot on the line, it is important to make sure you are pruning your evergreens properly. Read below for tips on how to trim your evergreen to have it looking its best.
First, remove any dead or diseased branches, trimming back to the closest healthy branch. For small branches, you can use sharp shears. Thicker branches will require a pruning saw. Next, prune your evergreen into the shape you desire. Start at the top to control its height. If you are looking for new growth, up to one-half of the plant's mass can be removed. Otherwise, remove enough branches to promote some new growth but not too many to dramatically alter the plant's aesthetic value. Repeat this process with the sides of the plant, making sure to cut each desired branch individually.
Even when seeking new growth, be sure to not over prune. Evergreens do not respond to trimming as quickly as many other plant types, so over pruning will result in a plant with long-lasting thinness. If you want to be safe, trim back just a little at a time to reach the desired shape gradually.
If your initial pruning takes place in spring, you may trim your evergreen again in the middle of the summer if need be. This second pruning is completed to control shape rather than to promote growth, as your evergreen should already be flourishing in the summer heat. Thus, do not over trim your evergreen in summer, removing just the branches that you consider overgrown. If your evergreen needs to maintain a crisp, clean look throughout the summer, you may prune it as often as necessary. Always water your evergreens immediately following any trimming.