How To Prune Evergreens

Evergreens are generally low-maintenance plants that need minimal pruning. In fact, many evergreens do beautifully with almost no pruning, other than to cut out the occasional damaged branch or two.

However, some homeowners like to shear their evergreens to give them a tight, clipped shape, as with hedges or yews and boxwoods trimmed into balls and boxes. This is purely a matter of personal preference, though, and not a requirement for healthy plants.

Not all evergreens take to shearing or hard pruning. Some, such as junipers and arborvitae, grow only on the outside. If you cut them back hard to get out what appears to be dead stuff, you'll be left only with trunk and branches and no needles and it won't grow back.

Boxwood, yew, and holly are notable exceptions. They can be trimmed hard and do beautifully (They're the evergreens used in topiary). They will regenerate even from the trunk.

Here's how to prune whatever kind of evergreen you have well:

1. Know the plant.

As a rule, the larger the leaf, the less pruning an evergreen shrub requires and the less it can withstand without ruining it. Broadleaf evergreens with big leaves, such as rhododendrons, aren’t well suited for shearing. Ragged, brown-edged foliage and blunted stems producing few leaves will result. They do better with minimal selective pruning (see below) where a branch is removed here or there.

If you want shrubs that can be clipped neatly into smooth forms, choose evergreens with naturally compact shapes, such as yews and boxwood. These shrubs have either needled foliage or small leaves.

2. Prune at the right time.

Needled evergreens can be trimmed at any time, except fall. Pruning tends to stimulate new growth and growth right before winter cold is likely to get zapped.

Winter, however, is an excellent time to prune since you can use the trimmings for holiday decorations.

Trim any evergreens that flower right after the flowers fade—if you trim much later you risk cutting off forming flower buds. Use a hand pruner to cut off the dead blooms and tips of small branches. This keeps plants from becoming leggy and overgrown.

3. Work with the plant's natural shape.

Know—or simply observe—the form of a plant before you prune. Many pyramid-shaped evergreens, for example, have a point at the end, a single branch that reaches upward, like the tip of a Christmas tree that you'd slip the star on. It's critical that when you prune that you do not trim off this point. The point directs the trees tapered upward climb. If you trim off the tip, the tree will start to fork at the top, distorting its graceful shape.

Some evergreens naturally grow low and spreading while others form globes. Still others are tall and vertical.

4. Decide what kind of pruning you'll do.

Selective pruning is simply going in and cutting out branches here and there. It removes wayward or too-long branches while retaining a plant’s natural form.

Simply reach inside the shrub and look to find where each long shoot emerges from stiff, older wood. Make pruning cuts here, inside the shrub, removing only the flexible shoot. (Cuts on stiff, older wood will not sprout again.) Do not leave any unattractive stubs protruding from the plant. Make your cuts toward the tops of plants where sunlight prompts the most new growth. Avoid pruning evergreens severely at the bottom where there’s less sunlight.

Shearing is done with a hand or power hedge trimmer and gives shrubs a tightly clipped, formal look. Shearing is done only on the surface, refining an evergreen's shape into the desired form. Plants suitable for shearing grow new twigs and leaves from each cut, making foliage thick and dense.

When shearing, be sure to stand back frequently to assess your work. Electric hedge trimmers can save time when you're shearing large hedges, but use care to avoid overdoing it.

Pinching, done on pines, spruces, and fir, helps control plant size and keeps these evergreens neat without browning the tips, which can happen with other pruning methods. Pinching is done by pinching or snapping off with your fingers the soft, new growth on nonflowering evergreens in late spring or early summer before the shoots “harden off,” becoming stiff and woody.