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.

View publication

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

Latest Resources

Should we treat ash trees for emerald ash borer?

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?

David C. Shaw | Apr 2023 | Featured question

Episode 32: Tree School (in English)

In this episode, Scott Leavengood visits the 33rd annual Clackamas Tree School to interview Sarah Cameron and Glenn Ahrens about what the event is and why it's so beneficial.

Scott Leavengood, Sarah Cameron, Glenn Ahrens | Apr 2023 | Podcast episode

Browse All Resources

Pruning videos

Pruning with the Pros - Thinning a canopy (in English)

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 (in English)

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 (in English)

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

Feb 2022 | Video

Pruning with the Pros - Removing a Wayward Branch (in English)

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

Are squirrels killing 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

How do I manage heat burn in trees and shrubs?

I live inland from the coast about 10 miles at the boundary of the Siuslaw National Forest, and yesterday's heat (99 degrees here) did severe damage to the forest trees, my blueberry bushes, rhododendrons, and most all of ...

Brad Withrow-Robinson | Jun 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

OSU Extension helps Oregon’s woodland owners manage their land

More than 600 volunteers have been trained through the Master Woodland Manager program.

May 2023 | Impact story

OSU Extension quickly mobilizes to respond to emerald ash borer discovery

Extension curated and disseminated essential information about the devastating pest and assist with initial monitoring efforts to determine how far and fast the insect is spreading in Oregon.

Kym Pokorny | Jan 12, 2023 | News story

Give overgrown trees a makeover with new OSU pruning video series

Knowledge is everything when it comes to pruning mature trees.

Kym Pokorny | Feb 18, 2022 | News story

All News

Explore more resources

Christmas trees

Cutting and selling trees

Forest health and management

Flowers, shrubs and trees

Urban forestry

Integrated pest management

Upcoming Events

Jun 10

Community Forestry Day - June 10, 2023

8:30 am - 2:30 pm Oregon City, OR

Meet Our Experts

Max Bennett

Forestry & Natural Resources

Alicia Christiansen

Forestry & Natural Resources

Dan Leavell

¿Tienes una pregunta? Pregúntale a Extensión

“Pregúntale a Extensión” es una forma de obtener respuestas del Servicio de Extensión de Oregon State University. Contamos con expertos en familia y salud, desarrollo comunitario, alimentación y agricultura, temas costeros, silvicultura, programas para jóvenes y jardinería.

Haganos una pregunta

Should we treat ash trees for emerald ash borer?

P: 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?

R: View answer | View all featured questions

See More Questions