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Urban Forestry
Arborist's Office
206-684-TREE (8733)
Street Tree Management Plan
Street Tree Planting Procedures
New Tree Planting
Tree Planting Tips
Trees Approved with Reservations
Watering Newly Planted Trees
Watering Established Trees
Urban Forestry Permits
Tree Service Providers
Tree Pruning Guide
Landscape Architecture
Seasonal Tree Care
Utility/Tree Inspections
Heritage Tree Program
Seattle Tree Inventory
Urban Forestry Class and Resources

New Tree Planting

See diagram below on how to plant a new tree.

The ideal time to plant a tree is when it is in a dormant condition, either in the fall, after leafdrop, or in early spring before bud-break. Weather conditions at these times are generally cool, and allow plants to establish new roots prior to having to endure the hot, dry conditions of summer. If trees have been properly cared for in the nursery or garden center, you should be able to plant a potted or balled & burlaped tree nearly any time during the growing season. Before you begin planting your tree, be sure you have had all underground utilities located prior to digging the hole. Call 1-800-424-5555 for utility location services at least 2 days prior to digging.

Dig a shallow, broad planting hole. Make the hole as wide as reasonably possible (as much as 3 times the width of the root ball), but only as deep as the root ball. You should have a minimum of 12" inches of loosened soil on all sides of the root ball. It is important to make the hole wide, as new roots will expand more quickly into loose soil. Most urban soils are compacted and unsuitable for healthy root growth.

Identify the trunk flare. The trunk flare is the part of the trunk where the roots spread out at the base of the tree. This point should be visible after the tree has been planted. If the trunk flare is not visible, you may have to remove some soil from the top of the root ball prior to planting the tree. This is critical in determining how deep the hole should be for proper planting. (See illustration below.)

Remove the pot or container from around the soil ball. If planting a balled and burlaped tree with a wire basket, cut the bottom out of the basket prior to placing the tree into the hole. It will be easier to remove the basket from the root ball prior to backfilling if you only have to cut the sides of the basket after it is in the hole.

Place the tree at the proper depth. Before putting the tree in the hole, check to see that the hole has been dug to the proper depth. The majority of the roots on a newly planted tree will develop within the top 12" inches of soil. If the tree is planted too deep, new roots may not develop due to lack of oxygen. It is better to plant the tree slightly high (1" to 2" above the base of the trunk flare), than to plant it at or below the original growing level. This will allow for some settling. To avoid damage when setting the tree into the hole, always lift the tree by the root ball, never by the trunk.

Straighten the tree in the hole. Before you begin backfilling, view the tree from several directions to confirm it is straight. Once you have begun to backfill, it is difficult to reposition.

Fill the hole with soil. Fill the hole about 1/3 full and gently (but firmly) tamp the soil around the base of the root ball. At this time, the wire basket can be removed, and all string and wire should be removed from around the trunk. Fill the remainder of the hole, taking care to pack the soil to eliminate air pockets that could cause roots to dry out. Water tamping (adding soil and settling it with water) is an acceptable, but messy, method of accomplishing this.

Stake the tree (if necessary). If the tree is firm within the soil ball, and the top is generally in proportion to the size of the root ball, staking may not be necessary. Studies have shown that trees will establish more quickly and develop stronger trunk and root systems if they are not staked at the time of planting. However, protective staking may be required on sites where lawn mower damage, vandalism or windy conditions are concerns. Support staking and ties should be removed after 1 growing season. A wide, flexible tying material should be used so that injury to the trunk is minimized.

Mulch the base of the tree. Mulch is simply organic matter applied to the base of the tree. It serves to hold moisture, moderate soil temperatures, reduce competition from grasses and weed and reduces mechanical injury from mowers and string trimmers. A two to four inch thick layer is ideal. Care should be taken not to cover the trunk of the tree with mulch, as it can cause decay of the bark at the base of the tree.

Follow up care. Keep the soil moist, but not soaked. Overwatering will cause leaves to turn yellow or fall off. Water trees at least once a week (unless significant rain is received), and more frequently during hot, dry weather. When the soil is dry beneath the surface of the mulch, it is time to water. Other follow-up care may include minor pruning of branches that were damaged during the planting process. Wait to begin corrective pruning until after the first season of growth in the new location.

Fertilization is not recommended during the first growing season. A low nitrogen, slow release fertilizer is suggested for fertilization in subsequent years.

For more information, call the City Arborist's office at 206-684-TREE (8733).

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