All trees are not equal: tips for tree selection
Mar 2013 06
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Donovan

Post by guest blogger Dr. Greg McPherson, a research forester with the USDA Forest Service’s Pacific Southwest Research Station located in Davis, CA. Greg chairs the ISA Urban Tree Growth & Longevity Working Group  and serves on the California Urban Forest Council’s Policy Advisory Committee. Read his full bio.

Trees do lots of good things for the environment, such as filtering harmful pollutants from the air and storing carbon dioxide (CO2), the leading cause of climate change. They also provide shade, which reduces the need for cooling and in turn lowers greenhouse gas emissions. Decreasing emissions isn’t just better for the environment—it’s a boost for your wallet, too.

As California Arbor Week approaches, you’d be wise to consider planting trees to help your neighbor and the environment. The first step toward successfully reaping all the benefits trees have to offer begins with careful tree selection and placement.

The following guidelines can help you select and locate trees that will maximize climate, energy and environmental benefits:

  • Consider native species. Native species are naturally adapted to your climate and provide habitat for wildlife. But not all natives are matched to the amount of soil moisture, sun, shade and other specific conditions at your planting site.
  • Choose local success. When using a native species doesn’t make sense, look around and see what old trees have done well in similar situations. Selectree, developed by the Urban Forests Ecosystems Institute at CalPoly, is a great resource for a tree selection. It is an interactive program designed to help you select appropriate trees based on compatible characteristics.
  • Dense wood holds more carbon. Wood density can vary tenfold among species. Trees with high densities such as oak, elm, ash and olive tend to hold more carbon. Visit the Wood Density Database to see how wood density varies.
  • Arbutus unedo_mature formBigger IS better. Large-stature trees have potential to store more carbon and cast more shade than small-stature trees. In a recent study we did in Los Angeles and Sacramento, we found that over half of those cities’ trees provide enough shade to significantly influence one or more buildings’ energy use. All of that shade adds up to a lot of savings.

Do keep in mind that large trees require a lot of space both above and below ground, so consider overhead or underground obstacles, such as power lines, sidewalks and sewer pipes, that could influence the tree’s growth or necessitate pruning.

  • Live long and prosper. Another aspect to keep in mind is life expectancy. Choose long-lived species that store carbon for generations to come. Most species with dense wood tend to be long-lived. Plus, wood from dead dense trees makes lovely furniture, boxes, benches, bowls, or other goods, which will store carbon for hundreds of years
  • West is the best. Locate trees to provide summer shade and block winter winds, reducing home energy consumption and associated greenhouse gas emissions. The best place for a tree is shading the west wall. For more recommendations on tree placement view our fact sheet.
  • Other considerations. Select trees that are not vulnerable to severe pests, drought and/or  storm damage. Planting a variety of well-adapted species over a period of time can also help reduce the risk of catastrophic loss from a single threat. Sycamore/plane has been identified as the most vulnerable variety in California. Look up the vulnerability of others here.

Tree planting 228Trees are valuable resources in combating many of our issues from pollution to energy to climate change, but we need to be smart and deliberate in our tree selection to get the greatest benefits. Have a happy Arbor Day and check out arborweek.org for ways to get involved.

Did this post make you wonder how much energy and carbon the trees on your property are saving you? Use ecoSmart Landscapes, a free interactive program developed by the USDA Forest Service’s Pacific Southwest Research Station, CalFire and EcoLayers.

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