I often get emails asking about the best time to prune. The answer is, it depends. Diseased, dead, or damaged branches can be pruned out at any time. Live growth has to be treated differently, however. When you prune live growth, you encourage new growth. This growth needs time to adjust. Don’t prune late in the fall, because the new growth will be exposed to winter before it has hardened off.

Evergreens can be pruned in the spring and summer. If you prune as the new growth is coming out, you can take off all the new growth. If you delay pruning until mid-summer, prune no more than two thirds of the new growth. I like to prune late in the winter or early spring, just before the new growth starts. This way the new growth hides the cuts.

According to Diane Relf of the Virginia Cooperative Extension Service, “Two basic pruning cuts are useful in pruning evergreens - heading and thinning. Heading refers to shortening a branch by cutting it back to just above a bud or smaller branch. Thinning involves removing a branch at its point of origin, which could be a trunk or the ground. Heading causes a proliferation of new shoots below each cut, and gives plants a stiff, formal appearance in the long run. Thinning creates gaps for light to penetrate thick foliage, and it results in a more open, informal effect that reflects an evergreen's natural growth habit. Use both techniques to control plant size and maintain attractive features.”

Certain plants such as Japanese Holly, Yews, and Boxwoods can stand a pretty hard shearing. The end result will look more formal, however. You can also prune these after they’ve grown for the season (in July or August) to maintain shape. I never use electric shears because they can tear the plants.

When pruning juniper, arborvitae, and other softer conifers, I’m very careful to prune one branch at a time. If you prune these rapidly, with shears, you risk creating an unnatural look to the plant.

The good news is, it’s pretty hard to kill a plant when pruning. You might end up with a misshapen plant, but often, over time, the plant will grow back. I suggest going slowly. Prune a little bit, step back after a few cuts to evaluate what you’ve done, and then prune some more.