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Here’s when and how to prune your trees in Arizona

Palo Verde (University of Arizona Photo)

When you live in the desert, the pruning of the trees in your yard raises a lot of questions: What time of year should pruning occur? Should they be trimmed, crowned, rounded or what?

John Eisenhower, a certified arborist with the International Society of Arboriculture, suggested homeowners look at standards set by the American National Standards Institute before pruning them or hiring someone to do the work.

Eisenhower, owner of Integrity Tree Service of Phoenix and a regular guest on Rosie on the House, said, instead of asking someone they hire to do trimming or cutting or rounding, homeowners should request pruning objectives, including minimum and maximum branch diameters and the percentage of foliage to remove.

Other concepts to remember:

Your trees probably need to be pruned at various times of year.

December through February is the best time to prune deciduous trees.

There is also a way to prune apples, peaches, nectarines, apricots and nuts to dictate the height of the fruit-bearing branches that can keep the fruit from being too high in the tree at harvest time.

Citrus trees need to be pruned after mid-February to avoid frost damage.

“Lion’s tailing” or “topping” should never be done to your trees.

These are improper pruning operations that make trees more vulnerable to sun and wind damage.

Topping is often done when trees grow taller and branches hit the house or hang over the roof. Tree owners think the only solution is to aggressively cut large stems to reduce the height or spread of the tree, but these cuts made at predetermined heights only encourage sprouting at the ends of the branches.

These large cuts are also the entry points for decay fungi to invade the tree.

A better method is to cut branches back to side branches at least one-third the diameter of the branches being cut. This reduces sprouting and leaves trees looking more natural.

In “lion’s tailing,” interior branches of a tree are over-pruned, leaving behind long slender limbs with a puff of foliage at the end that looks something like the tail of a lion.

This technique can lead to sprouting as well as sunburn on the trunk and lower limbs on super-hot days.

The heavy branch ends also collect the force of the wind and are more prone to breakage in storms.

For sun- and frost-sensitive trees, reduce the percentage of foliage that you remove.

During the middle of winter and summer, avoid pruning these trees altogether or only lightly shape them.

Citrus trees seldom need heavy pruning. It’s best that citrus branches grow down to the ground to shade their thin bark from the sun.

Most desert species should be pruned during the spring or fall.

Spring or early summer pruning of mesquite and other vigorous desert trees can prevent damage during the summer monsoon storms.

Palo verdes are more sun-sensitive, so avoid summer pruning and, as a rule, reduce their pruning dosage. Smaller and less vigorous desert trees that don’t require preventative monsoon pruning can be pruned in the fall.

Pruning later in the year tends to hold shape longer during the fall and winter months when tree growth slows down.

Be careful about elevating lower branches on young trees.

In an effort to get their bushy trees to look taller, homeowners often resort to cutting off lower branches too soon, but this only handicaps trees by robbing them of the energy reserves produced by those branches.

When you remove any live branch, you don’t promote growth in other parts of the tree, you simply reduce photosynthesis and overall health. Temporarily leaving lower branches on will accelerate the growth of upper branches.

When top branches begin to reach their mature height, you can start removing the lower branches, one or two each year until you reach the height of your lowest permanent branch.

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Rosie on the House

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