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How and Why to Prune Your Trees

September 16, 2019

tree pruningPruning and trimming your trees and shrubs is an essential part of yard maintenance, but it’s not quite as straightforward a process as mowing the grass. If you watch an arborist or professional prune a tree, it can seem a little like magic! Here are the basics of what you need to know about pruning your trees to keep them healthy, strong, and looking beautiful.

Why prune trees?

Many people use the terms “pruning” and “trimming” interchangeably. They are both important, but not quite the same. Pruning is the process of removing dead, broken, or infected branches from trees and shrubs. Trimming refers to cutting and shaping shrubs and hedges, mostly for design and aesthetic purposes.

Pruning is essential to keep the tree healthy and to remove unhealthy or dangerous branches. Pruning helps control the size and directs the tree’s growth in the way you would like. Thinning a dense canopy increases airflow and light, which helps combat diseases and lets more light through to the grass and plants below.

Experienced tree trimmers cut off crossing branches to prevent damage from them rubbing together. They also remove “co-dominant leaders,” or two equally dominant branches near the top of the tree. Cutting off one allows the other dominant branch to continue growing straight and prevents the branches from splitting and damaging the tree.

When to prune trees

Most arborists agree that you should prune away dead, diseased, damaged, deformed, and dying branches as soon as possible, regardless of the season or other pruning factors.

Before you decide when to prune your trees, determine when it blooms. Usually, the best time to prune trees is after the coldest parts of winter are over, when the tree is still “dormant.” This will promote healthy growth in the springtime.

If you have trees that bloom in the spring, it is best to prune them after their flowers fade. The trees that bloom in late summer should be pruned in winter or early spring.

In the summer, you can prune your trees to direct or slow the growth of limbs you don’t want to grow, or removing defective branches.

Fall is not an ideal time to prune because there are a lot of mold and decay fungi spores in the air. The spores can cause the tree to heal slower.

The “Five Factors of Form and Function” in pruning

According to Arbor Day Foundation arborist, Pete Smith, there are 5 factors of form and function. This gives some guidelines for pruning and will help the tree grow strong and healthy.

First, when you are finished pruning, two-thirds of the height of the tree should have branches and leaves in it. It is essential to keep the right number of branches with leaves on the tree so it will continue to grow at the right pace.

Second, the tree might not be able to recover well from too much pruning, so don’t remove more than one-third of the total number of branches in one year. This rule of thumb keeps you from getting too carried away.

Third, every branch that is attached to the main trunk should not be more than half the diameter of the trunk. If the branch is too thick in diameter, you should remove it.

Ideally, pruning cuts should be two inches in diameter or less. Sometimes it is necessary to cut larger branches, but you should do so cautiously.

Finally, you only want to make five total pruning cuts in one year. This will help develop a healthy and robust tree.

Use the “three-cut method” to protect your tree

Cutting large, heavy branches can be challenging and often, the branch falls off before you finish the cut, causing the bark underneath to tear away from the tree. This torn spot can allow pests and diseases to enter the tree, similar to an open cut on your finger or foot.

To avoid this, use the “three-cut method.” First, cut away all the lateral branches from the branch. This takes some of the weight off the limb and minimizes potential damage to the rest of the tree when the branch falls. Next, cut upward from the bottom of the limb. Try to cut about halfway through the branch but be careful not to get the saw pinched by the weight of the branch.

Make a second cut further out on the branch, sawing down until the branch breaks off. This will leave a much shorter “nub” on the tree trunk that you can easily cut off as close to the trunk as possible.

The right tools for pruning trees

As with any task, it’s essential to use the right tools to get the job done. Here are three must-have tools for keeping your trees trimmed and healthy.

Pruning Shears: Some people call them hand pruners. Pruning shears look a little like a pair of scissors and are ideal for cutting small twigs and branches up to about an inch in diameter. “Anvil pruning shears” have a straight edge so you should only use them on dead branches and twigs.

Pole Pruners: These handy pruners extend to reach those dead branches and twigs 10 to 15 feet up. They make pruning jobs much safer and easier.

Look for a pole pruner that has a bypass blade to cut branches about 2 inches thick and a pruning saw that can cut larger limbs.

Pruning Saw: Pruning saws come in different sizes and types to tackle all kinds of jobs. They have fine teeth to avoid damaging live trees.