We have plenty of reasons to love trees. They enhance our gardens, yards, fields and forests. Trees breathe in carbon dioxide and produce oxygen, keeping the atmosphere in balance. In summer, trees strategically planted around a home can significantly reduce air conditioning bills. Reduced energy demand means less pressure on the region’s electric power grid, which in turn means less fossil fuel carbon going into the air.
Research from the U.S Forest Service shows that trees provide shade for about 27 percent of urban areas. In addition to their shade benefits and contribution to the atmosphere, trees absorb and slow down stormwater runoff, provide bird habitat, extend the life of pavement, reduce noise pollution and provide privacy. Communitywide, shade trees help reduce the “heat island” effect caused by buildings and pavement, which absorb light energy and reflect it as heat.
According to Duane Northrup, Clark Public Utilities’ tree expert, a well-designed residential landscape using shade trees provides enough energy savings to return the initial investment in less than eight years.
Landscaping
How best to use trees around your home? Forest Service experts say to plant deciduous trees (those that lose their leaves in winter) so they will shade east-facing walls and windows from 7 to 11 a.m. and west-facing surfaces from 3 to 7 p.m. during June, July, and August. Trees with mature heights of at least 25 feet should be planted 10 to 20 feet east and west of the house.
Plant smaller deciduous, or evergreen trees with lower limbs, northwest and northeast of the building to provide late afternoon and early morning shade.
Trees can also be planted to shade paved areas. Light that strikes dark pavement like asphalt is absorbed, heating the air above. Light-colored pavement absorbs less heat, but can reflect it toward a building. Leaves reduce heat and reflection.
An outdoor air conditioning unit should be shaded from mid-morning through evening. Prune branches to allow at least several feet of clearance to encourage air flow.
What to plant, and when?
Spring in the cool, wet Northwest is the best time to plant trees. Once the danger of freezing winter weather has passed, trees can go in the ground. That gives them a good start on root growth before hotter, drier summer days.
Consult a local nursery expert to decide what trees best suit specific soil, yard layout and shade needs. Trees native to the region need the least maintenance and offer the most benefit. Among those are maple and juniper varieties, Western Mountain Ash and evergreens such as spruce and cedar. If you like songbirds, plant a dogwood.
There’s a long list of trees to avoid, including willow trees because their roots get into sewer pipes and septic tanks, box elder because of brittle limbs, Norway maple because of shallow root systems and black locust because their roots send up aggravating sprouts.
To avoid roof damage, work with a landscape professional or consult with your nursery expert to avoid planting your trees too close to the house. Make sure tree growth won’t interfere with power lines.
For more information, visit these websites:
• http://www.ext.colostate.edu/pubs/garden/07225.html
