Trees need pruning to control their size, to remove dead or broken limbs, and to remove dangerous limbs. The secret is to prune sparingly.

Watch for branches that rub against each other. This can cause a wound, a notch, or decay. Remove one of the branches when you find branches rubbing.

Sometimes trees can benefit from thinning. This means removing some of the lateral branches so that air and light can reach into the middle of the tree. By making the upper branches less crowded, more space is created for new shoots and leaves to develop. When you thin the top branches, make sure you never cut away more than one-third of the crown of the tree. The trim should look like a good haircut — it looks better, but you can hardly tell any work was done.

Your tree may need pruning to change its basic form, so that the tree can be stronger. When you examine your tree, look for the "leader" or main branch. Most shade trees should have only one leader.

A double leader can cause trouble in the long run by causing the tree to split in the crotch between leaders, and it presents a perfect place for decay to set in. If you have an existing tree with a double leader, go ahead and remove one of the leaders. Besides setting the stage for future decay, double leaders also can make a tree look lopsided.

Don't be confused by multi-trunk trees. A multi-trunk tree typically has three to five trunks coming from the ground, which is different than having two or more leaders developing a few feet above the ground.

When to prune
Here are guidelines for the best times to prune.

• Remove dead or damaged wood when you see it.
• Do major pruning in late winter. Wait until the coldest part of winter is over.
• You can do minor pruning in the summer, after most of the new growth is completed. This is a good time to remove branches that hang too far down. Summer pruning slows the tree's growth, but this is not a disadvantage if you want to keep your tree small.
• Prune flowering trees after they bloom. If they flower in summer or fall, prune in the winter. If they bloom in the spring, prune when the flowers fade.
• Prune while the tree is young. It heals better.
• Don't prune every year. Thin top branches every three to five years, and otherwise just remove dead or damaged limbs.

How to prune
The right tool for the job is important. Use scissor-type hand shears and loppers — similar to shears but with long handles — and a pruning saw. Keep them sharpened.

To remove a limb, use the "branch collar" pruning method. Cut the limb close to the main trunk but leave a small "collar" of the branch sticking up. This will allow the tree to heal more quickly. Do not leave large stubs on the tree.

When and how to prune your trees