Urban forestry

Announcements

Emerald ash borer permanent quarantine for Washington, Yamhill, Marion and Clackamas counties

The invasive pest emerald ash borer has been found in Oregon and a permanent quarantine prohibiting the movement of tree materials was issued for four counties. Read more...

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Trees to Know in Oregon and Washington

By Ed Jensen

For 70 years, people have turned to one book to learn about Northwest trees. This edition expands its scope, covering even more species of trees — including several rare species native to southwest Oregon. It also updates scientific names and adds a new section on how Northwest forests are likely to be affected by changing climates.

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Photo Credit: Setae - Adobe Stock (Cropped from original)

Latest Resources

Take care dealing with storm-damaged trees

The Colorado State Forest Service advises, "don't try to do it all yourself," when dealing with storm-damaged trees.

Jun 2025 | Online resource

First aid for storm-damaged trees

Storm-damaged trees can add up to big problems, but this guide from University of Missouri Extension advises people not to make any hasty decisions.

Jun 2025 | Online resource

Storm-related tree damage: steps to take before and after severe storms that may damage trees

Learn what precautions you should take, how to assess damage and when to call an arborist with this PDF from the International Society of Arboriculture.

Jun 2025 | Online resource

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Pruning videos

Pruning with the Pros - Introduction

In an ideal world, trees have been well pruned since planting, and only occasional maintenance pruning is needed. In reality, we often inherit mature trees in need of corrective pruning in order to serve their best function ...

Feb 2022 | Video

Pruning with the Pros - Tools of the Trade

A selection of tools that are needed for proper tree pruning in the landscape. With Oregon State University Extension’s Nicole Sanchez and certified arborists John Bellon and Tom Ford.

Feb 2022 | Video

Pruning with the Pros - Is this tree worth saving?

What a “volunteer” tree is in a landscape, its merits, and how it can be salvaged for a more attractive profile. With Oregon State University Extension’s Nicole Sanchez and certified arborists John Bellon and Tom Ford.

Feb 2022 | Video

Pruning with the Pros - When to get professional help

Some tree pruning issues that require professional help, and a demonstration of how a professional assesses a tree’s structure.

Feb 2022 | Video

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Meet Our Experts

Jennifer Killian

Urban Forestry Specialist

Sarah C. Low

Urban Forestry Specialist

Signe Danler

Home Horticulture Online Program Instructor

Contact for questions about Home Horticulture online. Submit other questions to Ask Extension, link below.

Brooke Edmunds

Community Horticulture, Master Gardeners

Contact me about the Master Gardener Program or gardening questions from Marion or Polk counties

Have a question? Ask Extension!

Ask Extension is a way for you to get answers from the Oregon State University Extension Service. We have experts in family and health, community development, food and agriculture, coastal issues, forestry, programs for young people, and gardening.

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Should we treat ash trees for emerald ash borer?

Q: I just read about the emerald ash borer (EAB) appearing in Oregon. We have two large very nice ash trees that we don't want to cut down, no signs of infestation at this time. Would you recommend we go ahead and treat these with the pesticide injection that treats for the borer, just in case?

A: View answer | View all featured questions

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