By Marilyn Loser: 2013 July 24
The sun beats down during the hot days of July in Alamosa. With only occasional cooling rains, it’s a good time to think about shade trees. I certainly seek tree shade on summer afternoons.
Have you ever noticed that it’s cooler under a tree than under an awning or porch roof? That’s because of the evaporative cooling of transpiration. Water is pulled through a tree’s trunk and stems to the leaves. As it evaporates from the leaf surfaces, it creates a measurable cooling effect.
You don’t need to stand under a tree to experience cooling. Properly planted, mature shade trees can make buildings up to 20 degrees cooler in the summer according to the Phoenix, Arizona, Shade Tree Program. The city of Sacramento, California, advertises that “once properly placed shade trees mature, you can save as much as 40 percent on your summer electric bill and help conserve energy during Sacramento's peak usage period.”
In addition to cooling us off, shade trees renew our air supply by absorbing carbon dioxide and producing oxygen. Each mature tree produces about 260 pounds of oxygen a year.
Phoenix and Sacramento are two of many cities that are taking urban forestry seriously. Both of these cities provide free shade trees to residents. That’s correct, free trees. Homeowners have to do their part.
In Phoenix folks have to attend a workshop to learn how to properly select, plant, and maintain trees. During the workshop community foresters help homeowners choose appropriate desert-adapted trees and select the best energy-savings locations around their homes. In Sacramento, residents can set up a visit from a community forester.
Sadly, in our small community we don’t have such a program. However, people can still plant and maintain shade trees on their property and reap the long-term rewards.
If you want to shade your home, you’ll probably want to plant a deciduous (sheds leaves annually) tree on the south or southwest of your house. If you planted an evergreen, the shade that would be welcome would not be so welcome during the cold winter. For more information on planting and caring for your shade tree, visit the Planting and Care tab at AlamosaTrees.net.
Due to Alamosa’s challenging climate, the pallet of appropriate shade trees isn’t as large as that for other Colorado cities such as Denver and Colorado Springs. Still, we have options. I look for cold-hardy trees (zone 3 if possible) that can stand our altitude (about 7,500 ft.), have a dense crown (usually medium to large leaves), and do well in our soil (mostly alkali and clay or sand). Since I don’t live near the Rio Grande, I also consider water needs.
I love Marshall Ash (also known as green seedless, “Fraxinus pennsylvanica ‘Marshall’) and it grows fairly quickly. We have two in our yard that are doing quite well. One is directly west of our two-story home. It’s taller than the roof line and has branches starting at eight feet from the ground. It gets regular water since it’s in the lawn. The second is planted amidst several garden beds and is mulched with gravel. I give it additional water several times during the summer. It is my favorite outdoor afternoon refuge.
If you have plenty of water, Lanceleaf Cottonwood (Populous x acuminata) is a good choice. Apparently, it suckers less than the Narrowleaf Cottonwood (Populus angustifolia) that I have. Both are rapid growers and provide abundant shade. But, I’m tired of continuously pulling up suckers that appear all over the yard.
Elms (Ulmus) are another good option in our area. I suggest American Elms (Ulmus americana) as they don’t seed prolifically and aren’t weedy looking. After so many years of drought, I not as opposed to well-cared for Siberian Elms (Ulmus pumila) as I used to be. Most survive even dry years; but if not given supplemental water are scraggy and known to drop limbs in the wind.
If I were planting a new shade tree I would also consider an Autumn Blaze Maple (Acer x freemanii ‘rubrum’), a Bur Oak (Quercus macrocarpa) or Western Hackberry (Celtis occidentalis). I don’t know of any large specimens in town. But the City of Alamosa and some residents have been planting them in the last few years.
The Maples in Cole Park and Zapata Park seem to be doing well. I think my property may be too windy and cold for them to thrive here. It seems to take a couple of years to get the Oaks established. I have one that is now doing well in my yard, but we lost a couple in city parks while others are doing well. The Hackberry in Jardin Hermosa is coming along well as is the one in my yard.
“Beautification be damned! Urban and community trees should be planted for economic, environmental and social reasons.” Donald C. Willeke