Q. We moved into our first home this past spring and absolutely love it - except for the huge evergreen shrubs that are almost completely blocking the front door! When is the best time to prune evergreen bushes, and how far back can I cut them?
A. The first step in pruning evergreens is to identify them, because they're not all created equal when it comes to pruning. To help you identify the evergreens in your landscape, click here.
Once you know which evergreens you're dealing with, I generally recommend pruning them between mid-June and mid-July. By then, their new growth has pretty much finished elongating, which allows you to get a sense of just how much of it needs to be removed to get the effect that you're looking for. Also, the follow year's buds will have not yet set.
This is especially important when pruning pines, as they set buds only at the tips of the current season's growth. If those buds are removed later in the summer or early the following spring, you'll leave a “stub” that will never put on new growth.
Meanwhile, you can significantly reduce the size of some overgrown evergreen shrubs without sacrificing their natural form by selectively removing just a few stems/branches in March or April.
In the picture above, for example, I'm removing a single large branch from the center of an overgrown juniper with handpruners in late April several years ago. Less than five minutes later, I had reduced the diameter of the plant by the better part of two feet by selectively removing five branches, at left.
Looking at the plant, it's difficult to tell that it had been pruned as I made the cuts where they would be hidden by the remaining branches. The cuts became even less obvious after the new growth had finished expanding in June.
This is in contrast to the appearance of many overgrown evergreen shrubs after they're hacked back to bare wood with hedge shears. The juniper at right, for example, was cut back hard with hedge shears because it was growing over the adjacent sidewalk. Unfortunately, the stubs that this process exposed will never produce new shoots.
Only yews (also know by their genus name, Taxus) are tolerant of really drastic pruning measures. By drastic, I mean that it's possible to cut back yews to nothing more than short stubs protruding off of the main trunk. While there are only extremely rare instances where I might recommend this, yews are tolerant of this practice because they can send out new shoots from dormant buds all along their stems and trunk, at left.