The right time to plant trees, shrubs, and many woody perennials in western Oregon and Washington is after the gentle fall rains start and before the ground has become too saturated to work without destroying soil structure.

Buy when you find something you love, but don’t plant it until the rainy fall season begins. In the Pacific Northwest, the dry summer is the harshest season for plants. Winters are generally mild, but the ground is too water-saturated to work. Spring can be soggy and the ground may not get dry enough for planting to allow newly planted trees and shrubs to establish before the dry season begins.

10-Minute University has many great resources about best practices for planting. A good place to start is Sherry Sheng’s video https://youtu.be/82-zMQjjxUE

There are challenges with planting trees and shrubs in the summer, watering being a major concern. Both the root ball and the surrounding soil must be kept evenly moist so that the new roots can grow beyond the root ball. Because of the differences between the root ball soil and the surrounding native soil, a barrier can develop and affect the water flow as well as hinder root expansion between them. Evaporation and water delivery methods during the hot summer months can also present challenges. Plants native to this area or similar climates elsewhere, are designed to sleep through the summer, not struggle with transplant shock and putting energy into new roots. These are good reasons in general to wait until the fall rains begin.

Other things to remember about planting trees, shrubs, and woody perennials:

  • Good soil is the foundation for healthy plants. https://clackamascountymastergardeners.org/10-minute-university/soil-planting/
  • Don’t dig when the soil is saturated; it destroys the soil’s ability to hold water and air. Hold a handful of soil in the palm and squeeze hard. If the soil ball readily falls apart, it’s time to plant.
  • For trees, shrubs and woody perennials, especially field grown, wash off as much of the original soil as possible from the roots so that they are in contact with the soil in the new location.
    https://gardenprofessors.com/why-root-washing-is-important-an-illustrated-cautionary-tale/
    https://csfs.colostate.edu/wp-content/uploads/2024/01/The-Science-of-Planting-Trees.pdf
  • Thoroughly water the plant immediately after planting to promote good contact between roots and soil.
  • Space according to the final size of the plant. This will eliminate having to move, prune or remove mature plants that are crowded or not thriving because of too much competition from other plants. Consult Sunset Western Garden Book and plant tag for plant characteristics, but keep in mind that mature size of the same plant depends on the location and growing conditions.
  • Group plants with similar water needs. Planting rhododendrons, manzanitas and lilacs together will guarantee unhappy plants. Sunset Western Garden Book includes an atlas of areas grouped according to multiple conditions and describes the requirements of thousands of plants.
  • Choose a location where ALL of the plant’s needs can be met: temperature (winter lows AND summer highs), light level, irrigation, appropriate soil and protection from other plants/insects and diseases/animals/people/cars. Right plant, right place.
  • Closely monitor the new plant for pest and disease. Weed, prune and harvest at the right time.
  • Have a plan and modify it as necessary. You’re the boss. https://www.youtube.com/watch?v=X4xB7enA-B8
  • Plant only what you really like and can take care of.

Click here for a printable pdf version of this article. Written by Justin Dune, August 2024. Photo courtesy Pixabay