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By Mona Kaiser
WSU Grant Adams Master Gardener 

Planting landscape trees


Have you decided what functions you want a tree to serve? Do you know which trees do best in our Columbia Basin area? Have you thought about how to properly plant your tree to ensure it survives and grows well? Do you know how to ensure good health and longevity for the tree you plant?

When you consider planting a tree, the first question you should ask is what functions do you want it to serve in your landscape? Will it be planted to provide shade, block a view, to improve the landscape around the house, or for the beauty? Start by thinking about what you want your yard to look like in 10 or 20 years. The key to analyzing a planting site is to envision it with a full-grown tree. Keep in mind that although your newly purchased tree will be only 5 or 10 feet tall at the time you purchase it, the tree may grow to 50 or 100 feet.

First, decide where to plant your tree. Let the planting location dictate the tree species you select, rather than the other way around. The placement of the tree is an important consideration. If you’re considering a shade tree it will need to be planted on the south or west side of the home to block the sun as desired. A large shade tree will grow 40 feet or more and should be planted 20 feet or more away from the house. Smaller trees can be placed closer. Always consider the mature height in relationship to power lines or other obstructions.

Before you purchase your tree, do your homework. Different tree species/varieties have certain requirements to be able to thrive in a landscape. 1) In the Columbia Basin, soils usually have a pH of around 7.5 and are more alkaline than acid. Some tree species prefer an acid soil type or may have other soil limiting characteristics so plant for the proper soil type. 2) Reference the USDA Plant Hardiness Map. The hardiness zone to purchase a tree for this area is Zone 5 or 4. 3) Our drying winds can be hard on some landscape trees so select a variety that can withstand this challenge. 4) Good reference material or a reputable nursery will have information about a tree’s susceptibility to particular insect or disease problems. Our local quality nurseries are willing to help us work through these difficult considerations when purchasing a tree, shrub or perennial. Some have their own website with a product list and more. Always check with your local nurseries or WSU Master Gardeners if you have questions.

In the Columbia Basin there are two preferred seasons to plant landscape plants; early to late fall (September through October), and in spring just after the ground has thawed until late May. Spring offers a much greater assortment of planting material to choose from, so this time of year becomes the preferred season for the homeowner to pick just the right tree to beautify their yard.

The way the tree is planted is extremely important for proper growth. Guidelines for planting the tree if it is sold as a bare-root tree (see diagram of tree without leaves), or sold as a balled-and-burlapped tree (see diagram of tree with leaves) are listed below. Always remove the burlap and twine. The burlap is treated to prevent rapid deterioration. The twine is nylon, which may girdle your tree if not removed.

Planting Guidelines:

1. Dig the hole large enough to accommodate the root system or root ball. When possible, dig a hole 2 to 3 times the width of the root system. The sides of the hole should slope toward the bottom of the root ball.

2. A swelling called the ‘trunk’ or ‘root’ flare is the area where the topmost roots join the trunk. The root flare (if visible) should be slightly above the surface of the soil when the tree is placed in the planting hole. Planting at the appropriate height will help assure the tree’s success. If you can’t see the trunk flare in a container-grown plant, remove soil from around the trunk until it becomes visible. If the tree is set too deep in the hole, remove it and firmly pack soil in the bottom of the hole. For bare-root trees, a cone of soil

in the center of the planting hole should help achieve this. (see diagram of tree without leaves)

3. Backfill using only native soil. Do not add any type of organic matter.

4. Create a basin to retain water by constructing a small berm around the planting hole. Water immediately after planting. Don’t overwater; roots should not be standing in water.

5. Use a mulch to conserve soil moisture, keeping slightly away from the trunk. If the soil around the root system of balled and burlap plant differs greatly from the native soil, gently fork some of the soil off the root ball and expose the roots (see diagram of tree with leaves, dashed line).

Planting and establishing trees is all about managing air and moisture in the soil. The three most common causes of poor plant establishment are: 1) planting too deep, 2) over watering, and 3) under watering.

Cooperating agencies: Washington State University, U.S. Department of Agriculture, and Washington counties. Extension programs and employment are available to all without

discrimination. Evidence of noncompliance may be reported through your local Extension office.

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