Question: Over the past five to 10 years it seems like summer lacks the occasional showers of previous decades, and the dry period seems to be getting longer each year. Because of this trend, I would like to plant more drought-tolerant trees in my landscape. Can you tell me the name of several trees that will grow well and survive in our area without regular irrigation?

Answer: I can share with you a large selection of drought-tolerant native and non-native trees with wonderful diverse characteristics. Keep in mind, even some of the native trees like Douglas fir are not drought-tolerant enough in our warming climate, especially if planted in low-elevation valley sites around Douglas County that lie between 400 and 600 feet above sea level.

Our climate in western Oregon can be stressful to trees that haven’t developed here and adapted. We have six months or more of saturated soils, followed by five months of bone-dry soils. This combination of too wet and too dry is not easy for most trees. Native trees have adapted to these conditions, which are likely to stress many non-native trees. And stressed trees are more susceptible to disease, insect infestation, and poor growth.

Bigleaf maple, madrone, chinquapin, Ponderosa pine, Incense cedar and Oregon white oak, also known as Garry oak, are all native trees that can tolerate our wet winters and dry summers. Since these trees are native to our state, they are all good choices for naturescaping to provide food and shelter to other forms of wildlife.

Research has shown that over 300 species of insects will spend part of their life cycle in our native oak trees. And often these species of insects provide a food source for our native songbirds. Without these native trees, our songbird population would decline or disappear.

If you prefer non-native trees, look for those that have similar characteristics to our natives that can tolerate wet and dry seasons and are not invasive. These would include catalpa (native to southeastern U.S.), gingko (China), honey locust (central and eastern North America), Atlas cedar (North Africa), Deodar cedar (Himalayas), mulberry (China), Swiss stone pine (central Europe), hornbeam (Europe to Iran and eastern North America), eastern redbud (eastern U.S.), and giant sequoia (Sierra Nevada).

To create a drought-tolerant, sustainable yard, plant drought-tolerant trees with other drought-tolerant plants in the same area of your garden. Don’t surround water-wise or drought-hardy trees with lawn, shrubs, or other plants that need frequent watering. Overwatering native trees during summer can lead to root rots.

To give new trees the best start, plant them during the fall or winter to allow their root systems a chance to get established before the heat of summer. Your drought-hardy trees will do better if you give them an occasional (monthly) deep irrigation during their first few summers in your landscape. And remember to put your trees in the right place. Know if your trees like full sun or shade, require a well-drained or damp site and if they will mature into a large or small specimen.

Steve Renquist is the Horticulture Extension Agent for OSU Extension Service of Douglas County. Steve can be reached by email steve.renquist@oregonstate.edu or phone at 541-672-4461.

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