How To Prune A Shade Tree

Whether a shade tree is large or small, there are some basic pruning principles to make sure it has the most attractive shape possible and that it isn't susceptible to splitting or breaking as it matures.

When it doubt, leave a tree alone. Most shade trees grow pretty well with minimal pruning. After all, they grow well in forests without any human intervention at all. Plus, bad pruning can distort the overall growth and risk the health of a tree.

Pruning Don'ts

In fact, bad pruning is enough of a culprit that it's important to know a few tree pruning "don'ts."

Don't top a tree. That is, don't just slice off the top of the tree to accommodate power lines or other obstacles. Utility companies over the years have been notorious for this but have gradually realized how much it harms the tree and ruins its visual appeal and as a result, most have changed their ways and now do more thoughtful pruning.

Don't plan on pruning a shade tree to control its size. This might work with a handful of evergreens, but with a deciduous tree, you're fighting a losing battle and will probably ruin the overall shape in the process. If you're planting, chose a tree that won't get any bigger than the desired size. And if you have a misplaced, oversized tree already on your hands, you might be better removing the tree entirely and replanting.

Don't be overly ambitious. If there are limbs to trim that are several inches across or are beyond the reach of a telescoping tree pruning tool (Fiskars® tree pruners extend up to 14 feet in length), it's probably worth it to call in a professional. You may have to spend some extra money but you could save yourself serious injury.

Don't rush it. Pruning is an art. Take your time; step back frequently to see the results of your work. Many gardeners like to prune a tree over a day or two so they can think about their strategy and cuts and look at it the second day with a fresh eye.

Simple Pruning

There are some types of pruning that are "no brainers." If you're hesitant about getting started on a pruning job, make the following cuts first:

Remove branches that are too low. Don't worry about small, newly planted trees but as they mature, shade trees should allow tall people to walk underneath without hitting their heads. "Limb up"—that is, trim off all lower limbs to a certain point—to permit this.

Removing damaged or dead limbs. Cut out dead wood—it will fall off eventually anyway and it invites insects to enter the tree. Also cut off broken or otherwise damaged limbs. They also invite in pests and diseases. All cuts should be clean, not ragged. Also, don't leave stubs—cut flush with the trunk or larger branch.

Trim suckers and water sprouts. These are slender, almost weedy new growths that when left unchecked will overwhelm the main tree. Suckers grow at the base of the tree or from the shallow larger roots. Water sprouts grow vertically along horizontal branches or sometimes from the main trunk. Both grow very rapidly and may need to be removed a couple—and maybe even four—times during the growing season. The larger you let them get, the more likely they are to recur.

More Complex Pruning

After you've made the simple, "no brainer" cuts, move on to these cuts that take a little more thought.

Remove any secondary leader. Shade trees should develop one strong central trunk. Sometimes, a large branch will start to grow vertically also, competing with the main trunk. This should be removed to encourage an attractive overall shape. Also, a secondary leader that has been allowed to grow large is prime to break off in an ice or wind storm, resulting in a tree that is ripped in half.

Prune branches that rub. Branches should not rub or they'll wear through the bark, inviting in pests or disease. Trim them accordingly to create space between branches.

Cut off deep crotched limbs that have weak connections. If there is a large branch that has a cracked or otherwise weak-looking connection to the trunk or other large branch, trim it off to prevent it from ripping off (perhaps along with a good portion of bark) in a storm or when a child tries to climb on it.

Remove larger limbs as needed. With smaller limbs less than a couple inches thick, you can simply clip them off with loppers or saw them off. Larger limbs need to be removed with more care.

First, cut off the limb in sections starting at the farthest reaches of the limb. You should end up with a stump a foot or two long.

Then, make an undercut to assure that the bark won't rip off as the branch falls. Go for a slightly outward sloping cut that follows the natural "collar" of the branch, the naturally occurring ridge around the base of the branch. This promotes better healing of the cut. Finally, make an overcut, coming downward as you saw. Again, cut outward at a slight angle to follow the crown of the branch.