Dear Jim: We are planning to landscape our new house. We like a wooded yard for cooling shade and also the idea of helping to reduce greenhouse gases. Where do we locate the trees and which are best? — Mark G.

Dear Mark: Wise landscaping can do more than just create a pretty yard. It can also lower your utility bills, in summer and winter, and improve your family’s comfort year-round. Trees, being one of the key components of any residential landscaping design, can have the greatest impact.

You mentioned greenhouse gases that come from burning fossil fuels. By having to run your air-conditioner less because your house is shaded with trees during summer, less coal, oil or gas is needed to generate electricity. Also, the evaporation of moisture from the leaves actually cools the air around your home similar to how perspiration cools your skin.

By taking advantage of passive solar heating during winter, with the proper placement and selection of trees, less natural gas, oil or electricity is used for heating. Trees, and all plants, use the only natural process to convert greenhouse gases (carbon dioxide) back into oxygen and carbohydrates.

The primary goal of efficient landscaping with trees is to shade your home during summer, yet allow the sun to pass through during winter. Other goals (depending on your climate) could be to allow cool evening breezes to flow around your house or to provide moisture for evaporative cooling.

Before you start your landscaping plan, check with a local landscaper to determine your temperature zone. This refers to the minimum winter temperature range. For warm climates in Zone 10, the range is 30 to 40 degrees. For cold climates in Zone 1, the range is 30-below to 40-below zero. If you select species of trees that prefer a climate more than one or two zones outside your range, they may not do well and may require excessive care.

In an average temperate climate, a typical efficient landscaping plan has deciduous trees to the south, southeast and southwest. The leaves block the sun during summer, but when the leaves fall during winter, the sun shines through to heat your home. Leave a small gap to the southwest to allow cooler evening breezes to reach your home.

Plant dense evergreens along the north, northeast and northwest sides. These block the cold winter winds. With the shorter days and the sun being lower in the sky during winter, not much solar heat comes from these directions.

In hot, humid climates, shading during summer is most important. Taller trees should be planted closer to your home to block the sun, which is higher in the sky. Leaving a gap for breezes is not as important. Avoid planting too many low heavy-foliage plants near the house because they may increase the humidity level.

Landscaping for hot, dry climates is somewhat similar, except plantings near your home are good. With the dry air, this creates evaporative cooling from the leaves.

source ; www.freep.com