Regional Gardening Reports :: National Gardening Association

In the Garden:
Southwestern Deserts
December, 2008
Regional Report

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Mexican buckeye in spring bloom at Boyce Thompson Arboretum in Superior, Arizona.

Top Ten Reasons to Plant a Tree

Do you ever notice how parked cars are often clustered around the relatively small patch of shade offered by a few trees dotted around a vast parking lot? We desert dwellers will trade those extra steps across baking asphalt for the chance to keep our car interiors from heating unbearably in direct sun. Of course, trees provide many more valuable attributes than cooling our cars before the drive home. Here are 10 great reasons to plant trees.

1. Reduce surrounding temperatures. Concrete and asphalt surfaces absorb sun during the day and radiate heat at night, which is called the "urban heat island effect." Phoenix and other Southwestern metro areas have documented higher temperatures in recent years as open space is gobbled up by development. Trees lower temperatures by providing shade and releasing moisture through their foliage, a process called transpiration.

2. Lower utility costs. Studies vary but most homeowners can save a chunk of change (up to 30 to 60 percent) on utility bills with well-sited trees. Plant deciduous trees on the east side of the house. In summer, their leafy foliage blocks the sun's rays. In winter, the sun shines through bare branches to warm your home early in the day. Low-water-use deciduous trees to consider include desert willow, blue palo verde, foothills palo verde, honey mesquite, and screwbean mesquite.

3. Reduce soil erosion. A U.S. Forest Service study in Salt Lake City showed that over a period of 12 hours, tree canopies reduced surface runoff by 11.3 million gallons (17 percent) in a one-inch rainstorm.

4. Provide beauty and color for your enjoyment. As space allows, add trees that offer seasonal interest year-round. For example, in winter, cascalote (Caesalpinia cacalaco) trees are loaded with fat yellow flower clusters. Spring features Mexican buckeye's (Ungnadia speciosa) flush of pink blossoms. (This tree is also commonly called Mexican redbud.) For a long season of bloom from spring through fall, consider desert willow (Chilopsis linearis). Chinese pistache (Pistacia chinensis) leaves turn brilliant shades of gold, red, or orange in fall. Its foliage can vary, so buy this tree in fall to get the color that you want.

5. Act as windbreak. Provide protection by planting trees perpendicular to the prevailing wind. This helps reduce energy use for warming or cooling the house, and also protects other plants from drying out in strong winds. In turn, this reduces outdoor water use on those plants.

6. Attract wildlife. Native creatures are adapted to native plants. The twisted form of hackberry tree (Celtis reticulata) provides nesting sites and shelter, food for seed eaters, and even serves as larval food for butterfly caterpillars.

7. Increase home value. Depending on the expert source, healthy, well-maintained trees can boost home prices 5 to 20 percent so it pays to keep them in good shape. If pruning is required and beyond your expertise, don't skimp on good maintenance. Obtain quotes from several certified arborists (not "Two Guys with a Ladder"). Ask who will actually be doing the work. And never "top" your trees!

8. Grow fruits or nuts. Depending on elevation, your landscape may support citrus, deciduous fruit (apples, apricots, peaches, plums, cherries, figs) and nuts (almonds, pecans). Check with your County Cooperative Extension to determine your area's average chilling hours and varieties that do well.

9. Extend outdoor living area. This can be as simple as a chaise lounge beneath a spreading canopy, beckoning you outdoors to relax after a long day.

10. Absorb air pollutants. There are numerous studies on the value of trees in absorbing carbon dioxide, sulfur dioxide, ozone, particulates and other pollutants. For example, according to the Trust for Public Land, one mature tree can absorb 48 pounds of carbon dioxide each year, while releasing sufficient oxygen into the atmosphere to support two humans. If each U.S. family planted one tree, the amount of carbon dioxide in the atmosphere would be reduced by one billion pounds annually according to American Forestry Association Tree Facts. Of course, we can dispute the accuracy of statistics, but it would be more productive to expend that energy on planting a tree!

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