Dear Jim: My parent’s yard has trees and their air conditioner seems to run less than ours. I know it takes years for trees to grow, but can you give me some tips on where and what kind to plant in our yard? – Sandra H.

Dear Sandra: It is not just your imagination your parents’ air conditioner runs less because of having trees in their yard. The Department of Energy has done sophisticated computer models showing just three properly placed trees can cut your utility bills by up to $250 per year.

There are many other benefits from landscaping your yard with the proper type and placement of trees. By shading your house, the walls, shingles, even curtains indoors, will last longer because the sun’s rays are blocked. The air immediately around your home will be less polluted and the oxygen level will be higher. Trees also create a sound barrier from road noise.

People often think of shading as the primary cooling effect, but trees also function as natural air conditioners through a evapotranspiration process. As the leaves on trees give off water, they cool the air similarly to how our own perspiration cools our skin. The air temperature near the house on a well-landscaped yard can be 10 degrees cooler than on a treeless one.

The key to efficient landscaping is selecting the proper species and placing them in the proper location for your specific climate. A well-landscaped yard in the hot, dry Southwest will look totally different from one in humid Georgia or in the Plains.

Draw a layout of your yard and decide where you need trees for your climate type. Also determine the height, shape, type (evergreen or deciduous), and growth rate of the trees. Next, talk with a local garden store expert to make sure you are planting trees which will thrive in your climate zone.

In a temperate climate, you will also be concerned about winter heating bills. Plant deciduous trees on south and west, leaving a small gap to the southwest for breezes. During winter with the leaves down, the sun will shine through. Plant evergreens on the north side for a winter windbreak.

In a hot, humid climate, you air condition more often. Natural breezes are good, but not as important as in a temperate climate. Shading is most important with tall trees to the south side. Avoid an overabundance of plantings, which will raise the humidity level and reduce the cooling effect.

In hot, dry climates, planting trees to shade the walls and roof is critical. Tall trees with a high canopy are effective. Lower plantings placed near the house are good because, with the dry air, the evapotranspiration process can create significant cooling.

Write for (instantly download – www.dulley.com) Update Bulletin No. 438 – showing diagrams of landscaping layouts for four climates, selector guide of 100 trees listing heights and shapes, growth rates, hardiness zones, and tree care/pruning tips. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.