Tree care

Trees to Know in Oregon and Washington

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: Stephen - Adobe Stock (Cropped from original)

Latest Resources

Episode 46: Storm Damage

In this episode, Lauren Grand is joined by Glenn Ahrens and Scott Altenhoff to discuss the impact of storms on Oregon's forests and preventative measures that can be taken to mitigate tree damage caused by storms.

Lauren Grand, Glenn Ahrens, Scott Altenhoff | Mar 2024 | Podcast episode

Alternative forest management series

There are many ways to manage forested lands. This series of case studies examines alternative forestry methods — from Individual Tree Selection to shelterwood harvest and group selection.

Jan 2024 | Collection

What is this fungus and could it indicate internal decay in my Douglas-fir?

A large fungus is growing at the base of a large Douglas-fir tree in my backyard. There are several fungi that can cause root rot in Douglas-fir, so I don't want to lose the tree, and I also don't want it to fall ...

David C. Shaw | Jan 2024 | Featured question

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Pruning videos

Pruning with the Pros - Thinning a canopy

Getting sunlight into the canopy of a tree can help provide good light penetration and air circulation, assist ripening in fruit trees, and is pleasing to look at. Join our pruning pros for a demonstration on thinning the canopy of a mature crabapple tree.

Feb 2022 | Video

Pruning with the Pros - Collars and Ridges

Identifying collars and ridge tissue in woody plants can help us determine the best places to make pruning cuts.

Feb 2022 | Video

Pruning with the Pros - Removing a Double Trunk

The best practice for removing a “double trunk” from a young landscape tree.

Feb 2022 | Video

Pruning with the Pros - Removing a Wayward Branch

How to remove a wayward branch that doesn't contribute to the structure and aesthetic of a tree. With Oregon State University Extension’s Nicole Sanchez and certified arborists John Bellon and Tom Ford.

Feb 2022 | Video

Featured Questions

Will wildlife damage my old growth juniper?

We have an old growth juniper on our property, and it has been taken over by squirrels. They have made their homes underneath the tree. I am afraid they will weaken the root structure, and the tree could fall over in ...

Dana Sanchez | Jul 2021 | Featured question

Is my cedar dying?

My beautiful cedars are now showing some dying branches. I’d like to send a photo to confirm if it has that fungus or beetle that’s killing lots of trees. And whether I need to cut them down before it gets dangerous to do so.

Glenn Ahrens | Dec 2020 | Featured question

Latest News

After five-year hiatus, Tree School East returns to serve forestland owners

The event drew 125 attendees, including participants, instructors, exhibitors and volunteers.

Jacob Putney | Mar 2024 | Impact story

Enthusiastic crowd attends OSU Extension workshop to hear about iconic madrone tree

With distinctive peeling bark and statuesque form madrone trees play an iconic role in the Pacific Northwest landscape.

Kym Pokorny | Dec 8, 2023 | News story

Don’t cut down that ash tree just yet – Oregon won’t see full effect of emerald ash borer for years

Currently, the emerald ash borer has been found in trees only in Washington County, where a quarantine prohibits moving ash (Fraxinus) or fringe tree (Chionanthus) wood in or out of the area.

Kym Pokorny | Jul 28, 2023 | News story

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Explore more resources

Christmas trees

Cutting and selling trees

Forest health and management

Flowers, shrubs and trees

Urban forestry

Integrated pest management

Upcoming Events

May 13

Native and Non-Native Insect Pests of Forest Trees: Diagnosis and Management

6:00 pm - 7:30 pm PDT Online

May 18

Conifers of the PNW: Characteristics and natural history of conifers in the pine family

10:00 am - 12:00 pm Portland, OR

May 20

Backyard Agroforestry: Sustainable Food Production in a Changing Climate

6:00 pm - 7:30 pm PDT Online

Meet Our Experts

Alicia Christiansen

Forestry & Natural Resources, Associate Professor of Practice

Dan Leavell

Micah Schmidt

Regional Fire Specialist, Northeast Region

Have a question? Ask Extension!

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What is this fungus and could it indicate internal decay in my Douglas-fir?

Q: A large fungus is growing at the base of a large Douglas-fir tree in my backyard. There are several fungi that can cause root rot in Douglas-fir, so I don't want to lose the tree, and I also don't want it to fall ...

A: View answer | View all featured questions

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