Tree & Planting Site Selection
Right Tree, Right Place
When selecting a tree species, think about how large the tree will grow over its lifetime and if your yard has the right sunlight, space and soil conditions for it to thrive. In particular, consider:
- Available space. Be sure that there is enough space for tree branches and roots to grow. Trees should be planted 5 feet away from underground water, sewer and gas lines. Plant trees at least 10 feet away from utility pole, 20 feet away from streetlights, and 7.5 feet away from your driveway. Large trees should be planted at least 20 feet away from your house or other structures.
- Tree size at maturity. The larger your tree is, the greater the benefits it can provide. However, before you plant a large tree you should be sure you have enough space for it. Trees planted under power lines should be less than 25’ tall at maturity. Check out SDOT's small tree list for species ideas.
- Utilities. In addition to powerlines, trees should be planted at least 5 ft. from underground utility lines, 10 ft. from power poles, 20 ft. from street lights or other trees, and 30 ft. from a corner curb. To locate your underground utilities, be sure to call 811 to submit a dig ticket at least two days before you plan to dig.
- Evergreen or deciduous. Evergreen trees, which hold their leaves year-round, trap far more stormwater runoff than do deciduous trees, helping keep our waterways clean. Evergreen trees also add year-round interest to your yard. When it's appropriate, consider planting an evergreen tree.
- Tree form/shape. Small, spreading trees that are multi-stemmed require regular pruning when planted near a sidewalk or road, however work well in yard spaces. Upright trees can be better trained to grow over pedestrian and road traffic.
- Summer growing conditions. Does your site need a tree that can handle drought or flooding? You should also consider how much sun your new tree will receive in its new spot. If your planting location is shady, be sure to plant a tree that will grow in part or full shade.
- Soil. Poor soil is a problem in urban areas and often limits the success and health of trees. Compacted soil and soils with high clay content can have poor drainage, which lowers the oxygen and can lead to standing water. If you are concerned about your site's drainage, dig a 1 foot deep hole and fill it with water. If it hasn't drained within an hour or two, your site has poor drainage and it is very important that you select a tree that can handle staying wet during the winter months, such as a bald cypress (Taxodium distichum) or black tupelo (Nyssa sylvatica). Click here for more on soil.
- Street tree permits. If your new tree will be in the planting strip or right of way, you need to apply for a free permit from SDOT. You can obtain a permit by calling (206) 684-TREE or clicking here. If you want help with the permitting process, consider participating in Trees for Neighborhoods.
- Non-invasive species. Select tree species without invasive tendencies in our region. Avoid English laurel (Prunus laurocerasus), English holly (Ilex aquifolium), European hawthorn (Crataegus monogyna), and tree of heaven (Ailanthus altissima). These trees are known to spread into Seattle's parks and open spaces and compete with native species.
Native trees are great, but ornamental trees are also appropriate as long as they are not invasive. Some non-native tree species and cultivars are actually more adaptable to Seattle's urban environment and require less care than native species. If you're confused about the difference between native, non-native, and invasive trees, check out this great overview from the Oregon Department of Forestry.
- Maintenance. Consider the future maintenance requirements of a given tree. All young trees need to be watered during summer through establishment, or roughly the first 3-5 years. Fruit trees are great, but only plant if you're willing to pick up dropped fruit and leaves each fall.
Consider Planting a Large Tree
We love large trees! Not only do large trees become treasured neighborhood assets, but research has shown that large trees provide our cities with the most benefits. They provide higher quality habitat for birds and other wildlife and they have larger root systems to help stabilize hillsides and prevent erosion. Large trees do more to buffer weather conditions, providing shade on hot days to reduce the need for air conditioning, and blocking winter winds to help save on heating bills. Studies have also shown that large trees even increase residential and commercial property values!
Large evergreen trees, especially conifers, are even better. Because large conifers grow so tall in our region, they produce a larger volume of leaf area on a smaller footprint – using the same amount of yard space but working harder to take in carbon dioxide, produce oxygen, and filter out air pollutants. And because evergreens hold their needles and leaves through the winter, our rainy season, they reduce stormwater runoff to a much greater extent than do small deciduous trees.
If you have the space in your yard or planting strip (away from overhead power lines), consider making a long-term investement in your neighborhood by planting a tree that will give back for decades!
Tree Selection Resources
Demystifying the Art of Tree Selection
Great Plant Picks - Lists over 100 excellent trees that thrive in Seattle and are resistant to pests and disease.
Street Tree Planting List
Seattle Master Tree List
King County Native Plant Guide
City Fruit's Guide to Best Fruits in Western Washington
Email TreesforNeighborhoods@Seattle.gov or call 206-684-3979 for questions about tree or site selection.