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Plant deciduous trees with broad, leafy crowns on the south, east or west side of a house to shade it from sun in the hotter months. (photo by www.shutterstock.com)

Trees offer us a host of environmentally friendly qualities.
Here are ways to return the favor when we plant them.

By Sara Bruskin

Autumn is famous for its harvest-themed hooplas, but before that hard cider goes to your head, remember that harvest time for some is planting time for others. This time of year is great for planting trees, as it’s easier for root systems to grow when the air has chilled but the soil is still warm. (There are exceptions to this, so be sure to check the planting recommendations for your specific tree to confirm the ideal planting season.) Planting trees is a big environmental boost for the planet, but there are extra steps you can take to make sure your new addition is especially environmentally friendly.

Choose Natives

Tree of heaven (Ailanthus altissima) is one of Colorado’s worst invasive trees. It can even grow in cement cracks, and one even survived the blast at Hiroshima! It’s best to plant native trees that have evolved to survive and thrive here. If you must plant a non-native tree, first be sure it’s not an invasive species. (photos by www.shutterstock.com)

Planting trees that naturally grow in your locale helps to conserve water and avoids excess fertilizer use because that species has evolved to survive and thrive in Colorado. Testing the soil around your house is still a good idea, as the conditions in your landscape may be more compatible with some native trees than others.

If you desperately want a tree that isn’t native to these parts, make absolutely 100-percent sure it is not considered invasive to this area. Invasive species can decimate ecosystems, and we already have some serious offenders here. Some of Colorado’s worst invasive trees are the Russian olive, tamarisk, Siberian elm and tree of heaven (Ailanthus altissima). Tree of heaven is so hard to kill that one managed to survive in Hiroshima less than 1,000 feet from the atomic-bomb detonation in 1945—and it still grows there today. The species also contains chemical compounds that can be hazardous to plants growing nearby, so be careful about planting trees that are not explicitly recommended by local arborists.

Don’t Be Vulnerable

Dustin Brown, of Boulder’s Blue River Forestry & Tree Care, recommends planting trees that aren’t prone to diseases and pests. “This will help prevent the need for future pesticide applications,” he says. “While there are botanical and organic options for treating harmful pests and pathogens, the best way to avoid using them is through proper tree-species selection and promoting local tree diversity.”

Pesticides are extremely toxic to the environment, so planting trees that won’t need these treatments gives you major green points. Because we can’t always anticipate which trees will be the target of new bugs and blights, ecological diversity is a must. If your neighborhood is all Rocky Mountain maples, pick something else to plant. Ecosystems are strongest when they have a lot of variety, since different species are susceptible to different attacks and a wide range of trees means a greater chance of survivors when bad times roll around.

Above: Avoid planting trees susceptible to diseases and pests, like this ash tree that fell victim to emerald ash borers. (photo by www.shutterstock.com)

Perfect Placement

Dense wind-blocking evergreens can shield a home from winter winds when planted on the north side of a house. (photo by www.shutterstock.com)

The most important thing to consider when it comes to planting is making sure the tree can survive in a given location. But strategically placing trees around your house can also make a big difference in home energy use. Deciduous trees with broad, leafy crowns should be planted on the south, east or west side of a house to shade it from sun in the hotter months, whereas dense wind-blocking evergreens can shield your house from winter winds on the north side of a home.

However, make sure you don’t plant trees with large crowns or root systems too close to your house, as branches can damage the roof, and roots can cause foundation issues. If you need to frequently prune branches or dig down to manage root systems, the necessary machinery to do these tasks will burn the fossil fuels that you’d theoretically saved through a tree’s heating and cooling effects.

Gas Gobblers

If you want to select a tree specifically for its ability to combat climate change, there are three things you’ll need to consider: efficiency, space and life span. Some trees naturally take in more carbon dioxide and chip away at greenhouse gas levels more efficiently. In Colorado, some of the best carbon-containing trees are ponderosa pines, Douglas firs, aspens and oaks. Because the carbon-containment capability of any given tree increases with its size, plant the largest tree that your space will allow (but again, keep pruning and other maintenance requirements in mind).

photo by www.shutterstock.com

The life span of your tree matters because plants don’t magically eliminate greenhouse gases; they simply contain them. Trees convert carbon from the atmosphere into woody biomass in a process called carbon sequestration, but that carbon will be released if the wood burns or rots away. A longer-living tree sequesters more carbon for a longer period of time.

On the same topic, if you need to remove an old tree from your yard before planting a new one, try to find someone who can use that wood for furniture making so the carbon remains sequestered for even longer.

Irrigation & Nutrition

Once established, native tree species should be fine without additional watering, but newly planted trees need some help. Installing drip lines is the best way to water trees. Drip systems use less water over a longer period of time, so the water gets fully absorbed by the tree rather than pooling and creating runoff. Blue River’s Brown suggests installing additional drip lines in a larger radius around the tree in anticipation of future root growth. “Keep in mind that the magic happens out on the tips of the roots,” he says, “so it’s important to keep that area hydrated.”

Planting trees is great on many levels, but do it right. The tree pictured above was planted incorrectly. The mulch should be in a circle 6 inches away from the trunk—not touching it. (photo by www.shutterstock.com)

He also recommends creating mulch rings around trees to help maintain moisture “and facilitate the reproduction and growth of healthy microorganisms around your trees’ roots.” To mulch correctly, apply enough mulch to create a ring 3 to 4 feet in diameter around the tree, at a depth of 3 to 4 inches, says Alison O’Connor, horticulture agent for the Colorado State University Extension. But keep the mulch 6 inches away from the trunk. “It should form a nice circle around and away from the trunk,” she says.

If you feel like your tree needs additional nutrients, Brown’s go-to solution is compost tea, which he says introduces beneficial microorganisms and mycorrhizae (a fungus that grows in association with roots) to the soil and roots. “Which makes it a great alternative to chemical fertilizers,” he adds. The less we chemically mess with our trees, the more sustainable and environmentally friendly they’ll be.

With all of these variables, the perfect tree planted in the perfect place may seem like an impossible goal, but remember—planting a tree in general is a huge environmental benefit, and Boulder County is full of eco-conscious landscapers who can help you. The U.S. Forest Service has resources to guide you at www.fs.fed.us/learn/trees, and the Colorado State University Extension at www.cmg.colostate.edu/pubs/trees.html has useful information on everything from species and watering to diseases, fertilization and more.

Happy planting!