Pruning Trees
Trees are the most valuable elements of a landscape, for many reasons. They add structure, form and character. Many add seasonal color and shade. They provide the framework from which to build a balanced, pleasing landscape. Deciduous trees provide shade in summer, then allow the sun to shine through their branches in winter. Evergreen trees are in leaf all year and serve as windbreaks and screens for privacy.
When you plant trees, be aware that they require more care when young and less and less as they mature. Arid land trees have different requirements compared to trees grown in temperate climates with abundant rainfall.
Pruning Young Trees
When pruning young trees – those three to four years old – the goal is to establish strong girth or width in a single-trunk tree. The stronger the trunk, the more apt it will be able to grow without stakes. If you are growing a multi-trunk specimen, your goal should be to develop three to four strong leaders.
To develop strong trunks, do not remove lower branches. They “feed the trunk in the area and protect bark from sun damage. Leave these lower branches in place for a few years. They can then be pruned up for a more refined look or to allow for pedestrian traffic beneath. Trim the interior to establish the desired branch spacing. Your goals should be to reduce the potential for wind damage while also increasing penetration of light. Remove branches that are dead, weakened, injured, diseased, or damaged.
Protect the trunks of young trees from high heat and intense sunlight. If trees produce heavy canopy growth, this is often enough to shade the trunk. Unfortunately, most side branches on single-trunk trees grown in containers are removed at the nursery. Low side branches are often left on multi-trunk trees. If trunks require protection from sunburn apply white latex paint diluted by half with water. Commercial tree trunk paints are also available.
To thin young trees as well as mature trees, selectively remove branches. You want to improve structure, control unwieldy branches, “lift up” lower branches by removing them from the trunk and thin the interior to decrease wind resistance. Improving branch spacing also preserves the tree’s natural shape.
Don’t prune too much at one time, especially during the summer in hot climates. Pruning removes leaves, branches, buds and stored energy, all of which benefit the tree and are needed for proper growth. Removing too many branches also increases susceptibility to pests, slows growth, undermines health and stimulates excessive sprouting.
Topping Tall Trees: Avoid!
In the West, certain trees such as Brachychiton populneus, bottle tree, tall-growing Eucalyptus species, and Populus species, poplar, are commonly planted where their height and vigorous root systems create serious problems.
In many situations the ultimate height, spread, rate of growth and pruning needs were not matched to the site. In addition, if large trees are not maintained regularly, major problems tend to develop. Aging branches can break and fall.
Information courtesy of ‘Johnson’s Guide for the Arid West’
For more informative answers to questions contact the University of Arizona, Maricopa County, Cooperative Extension Service at (602) 470-8086.