Arbor Month in Parks & Recreation

Lake Oswego: A Tree City USA for 37 Consecutive Years

Thank You for Celebrating Arbor Month with Us!

Here we are—another year of Arbor Month activities and information. Each year, we partner with the Planning Department to celebrate Arbor Month. Click below to explore the full lineup of activities and ways to get involved.

Click here to be connected to all the Arbor Month Events.

With the support of our Parks & Recreation and Planning Departments, community volunteers, local organizations, and dedicated staff, we celebrate Lake Oswego’s 37th consecutive year as a Tree City USA. Together, we also recognize our continued growth with the Tree City USA Growth Award. From tree plantings to nature walks and educational outreach, these efforts strengthen our urban forest and deepen our shared commitment to sustainability.

A special shout out to Ranger Ben and our creative Parks team for their engaging videos and social media highlights throughout the month.

This year we are focusing mostly on Heritage Trees. Follow along to learn about their history, locations, and the many unique species that help define Lake Oswego’s landscape. You might even see a few special guests along the way.

Stay tuned each week as new videos are released. Week One is now live. See the right side of this page!

Tree of the Week Series

Celebrate Arbor Month with our Tree of the Week series, highlighting some of Lake Oswego’s most notable trees and the stories that make them unique.

Week One: Peg Tree (Douglas Fir)

This was recognized as Heritage Tree #5 in 1998 and measures in at 69” DBH (diameter at breast height.) It is a Douglas Fir, but it has been named The Peg Tree. It earned its name because a peg was driven into the trunk to hang a lantern and early town hall meetings and Sunday school were held underneath the tree. 

Week Two: Deodar Cedar

This was recognized as Heritage Tree #2 in 1998 and measures in at 56” DBH (diameter at breast height.) Deodar cedars are native to the Himalayas and are known for their dropping branches and gray-green needles. These trees are often called “Wood of the Gods” as they were historically revered and used to build temples. 

Week Three: American Elm

This was recognized as Heritage Tree #23 in 2010 and measures in at 71” DBH (diameter at breast height.) It is the only American Elm tree listed as a Heritage Tree in the City.  American Elms once lined nearly every main street in the country before Dutch elm disease (DED) devastated populations in the 1930s. DED has killed roughly 75% of American elms in North America, reducing the typical life span of these trees from over 200 years to less than 30.

Week Four: Giant Sequoia

This was recognized as Heritage Tree #43 in 2024 and measures in at 78” DBH (diameter at breast height.) Giant sequoias are the world’s largest trees by volume and can be found on the western slope of California’s Sierra Nevada. They can live over 3,000 years and grown over 300 feet tall.  

Week Five: Oregon Ash

While not a designated Heritage Tree, the Oregon ash is the only ash species native to the Pacific Northwest. They can grow up to 80 feet tall and are often found in wet, riparian soils. They are currently being threatened by the arrival of Emerald Ash Borer (EAB) in the state of Oregon. EAB is considered the most destructive forest pest in North America, with nearly a 100% mortality rate for untreated ash trees. EAB was first detected on the West Coast in Forest Grove, OR in June 2022.