April is Arbor Month!

Arbor Day is America’s National Tree Holiday, observed on the last Friday of April to celebrate the role of trees in our lives and to promote tree planting and care. Here in Lake Oswego, we celebrate the entire month of April as Lake Oswego Arbor Month. Click here to read the City’s proclamation.

For 37 years, the City of Lake Oswego has earned Tree City USA (TCUSA) recognition from the National Arbor Day Foundation for demonstrating a strong commitment to managing and caring for trees. Cities earn TCUSA status by meeting four standards: maintaining a tree board (the Parks, Recreation and Natural Resources Advisory Board), having a tree ordinance, spending a minimum $2 per capita on urban forest management, and proclaiming and celebrating Arbor Day annually.

This year, the Arbor Day Foundation also presented Lake Oswego with its ninth TCUSA Growth Award, which recognizes innovative projects and higher levels of tree care by participating Tree City USA communities. The Growth Award was awarded to the City for hiring an Urban Forester for the first time. Lake Oswego’s first Urban Forester, Courtney Wilson, joined the City in October 2025.  Creating an Urban Forester staff position to oversee the management, maintenance, and evaluation of the City’s urban forest in the public right-of-way and on public lands, through collaboration between various City departments (Parks, Public Works and Planning), was a recommended action item in the 2024 Urban and Community Forestry Plan Update.

Each week during Arbor Month, Parks & Recreation invites you to explore a “Tree of the Week” by highlighting Heritage Trees that add beauty, diversity and significance to our community. Check them out, visit these unique trees yourself, and find other fun ways to celebrate trees this Arbor Month below. 

Urban & Community Forestry Events:

TRILLIUM FESTIVAL
Saturday, April 4, 9 a.m. to 3 p.m., Tryon Creek State Natural Area, 11321 SW Terwilliger Blvd.
Join Friends of Tryon Creek for the 46^th Annual Trillium Festival, a festive day in the woods to celebrate the return of the Trillium, an early season perennial native to our local forests. In addition to the Native Plant Sale, this family-friendly event includes a Gardening Resources Fair and free interactive nature stations in the classroom and on the trails. More event details are available at www.tryonfriends.org/calendar.

BE A TREE HERO 
Help Oswego Lake Watershed Council restore and enhance treasured woodlands around town this Arbor Month. Come learn about woodland ecology and lend a hand for a healthier habitat by removing invasive English ivy.  Capacity is limited and registration is required. Visit www.oswegowatershed.org/volunteer-calendar/ to learn more or scan this QR code for quick access to register for all upcoming Oswego Lake Watershed Council events:.

• Westlake HOA Work Party, Saturday, April 4 from 10 a.m. to 12 p.m.
• Woodside Circle HOA Work Party, Saturday, April 11 from 10 a.m. to 12 p.m.
• Mountain Park HOA Work Party, Wednesday, April 15 from 9 a.m. to 11 a.m.
• Mountain Park HOA Work Party, Saturday, April 18 from 9 a.m. to 11 a.m.
• Beth Ryan Nature Preserve, Saturday, April 25 from 1 p.m. to 3 p.m.

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SPRING WATERSHED RESTORATION TOURS
The Oswego Lake Watershed Council invites you to step into the landscape and experience the watershed firsthand through a guided Watershed Restoration Tour Series beginning on April 11. Each one-hour tour will explore how local restoration projects support healthy streams, resilient urban forests, and climate-ready communities. Come explore the watershed, connect with your community, and discover how restoration work is building a healthier, more resilient future for Lake Oswego. Each tour is held at a different location within one of two restoration sites and highlights different restoration strategies and ecological features. Visit www.oswegowatershed.org/spring-watershed-restoration-tours/ for more information and to sign up and complete the required waiver form.  

• Mountain Park: April 11 at 1 p.m. | May 9 at 1 p.m. | June 13 at 1 p.m.
• Westlake: April 25 at 10 a.m. | May 23 at 1 p.m. | June 27 at 1 p.m.
   

HALLINAN SCAVENGER HUNT
Saturday, April 18, 9 a.m. to 11 a.m., 1103 Obrien Street, street parking only
Gather the whole family for a fun-filled Nature Treasure Hunt in beautiful Hallinan Woods Park! Explore the park's natural wonders as you search for hidden treasures. This event is open to adventurers of all ages and all materials will be provided. This event is free and no pre-registration is required but please arrive on time for instructions. Contact Kaleb Simpson, Natural Resource and Stewardship Coordinator at stewardship@lakeoswego.city with questions.

ASH AND OAK WORKSHOP
Saturday, April 18, 9:30 a.m. to 12:30 pm, Education Pavillion at Tryon Creek State Natural Area, 11321 SW Terwilliger Blvd
Join the Oswego Lake Watershed Council for a free workshop to support forest health and preparedness. Learn how to identify signs and symptoms of emerald ash borer and mediterranean oak borer and how these invasive insect pests threaten the urban forest from local experts including ISA Certified Arborist Brian French. Registration is required. Learn more at www.oswegowatershed.org/tree-health-workshops/.

SUSTAINABILITY RESOURCE FAIR
Sunday, April 19, 1 p.m. to 4 p.m., River Grove Elementary School, 5850 SW McEwan Road
In celebration of Arbor Month and Earth Day, the City of Lake Oswego Sustainability Advisory Board, Lake Oswego School District, Lake Oswego Sustainability Network, and Oswego Lake Watershed Council are holding the 5^th Annual Lake Oswego Sustainability Resource Fair. The theme for this year’s fair is Sustainability in Action, featuring hands-on ways to live sustainably and help our community thrive, including information on native plants and pollinators, kid-friendly crafts, battery powered yard tools, EV vehicles, and more. Find details at: https://www.ci.oswego.or.us/sustainability/sustainability-resource-fair-2026.

OAK TREE WORKSHOP
Tuesday April 21, 9 a.m. to 12 p.m., 2 Mt Jefferson Terrace
Join the Mountain Park HOA Landscape Department, Oswego Lake Watershed Council, and ISA Certified Arborist Brian French to learn about Oregon white oak health and how to identify signs and symptoms of mediterranean oak borer, an invasive insect pest recently discovered in Oregon. Then, practice being a community scientist by surveying Oregon white oaks to help track and intercept threatening pests and contribute to a better understanding of the urban forest. Register for this workshop at: https://forms.gle/rNNT5ikZ6qpRJ4kj6.

SPRINGBROOK PARK PRESCHOOL NATURE WALK
Wednesday, April 22, 10:30 to 11:30 a.m., Springbrook Park, park at Uplands Elementary School or along the street, 2055 Wembley Park Road, meet at the Park kiosk behind the playground
Preschoolers can join Friends of Springbrook Park for a fun and interactive nature walk through Springbrook Park. Exploration buckets will be provided for hands on discovering. This event is free and no pre-registration is required. Preschoolers need to be accompanied by an adult. Contact Anne Lider at anne.lider@springbrookpark.org with questions.

TREE PLANTING WORKSHOP
Saturday, April 25, 9 a.m. to 11 a.m., Westlake Park, 14165 Bunick Drive, meet under the covered shelter along Bunick Drive
Celebrate Arbor Month by planting trees with Parks and Recreation staff at Westlake Park. Learn what to look for in selecting a high-quality tree and practice proper tree planting techniques. Dress for the weather and wear closed-toed shoes. Pre-registration is required and capacity is limited to 25 participants. Contact stewardship@lakeoswego.city with questions and visit www.ci.oswego.or.us/planning/workshop-series or call 503-635-0290 for free registration.

TREE PRUNING WORKSHOP
Saturday, April 25, 10 a.m. to 12 p.m., Foothills Park, 199 Foothills Road, meet at the pavilion
Understand why, what, and how to prune to develop healthy, strong, and attractive trees and shrubs. Explore pruning types, proper cutting tools and techniques, and tree responses to pruning. This workshop is led by ISA Board Certified Master Arborist Rick Till. Pre-registration is required and capacity is limited to 40 participants. Visit www.ci.oswego.or.us/planning/workshop-series or call 503-635-0290 to register.

BUG BIOBLITZ: CITY NATURE CHALLENGE
This year, the Bug BioBlitz will take place as part of the City Nature Challenge, a global community-science event that invites participants around the work to observe and record as many wild plants, animals, fungi and insects as possible over a four-day period using the free iNaturalist app. Whether you explore your own backyard, a neighborhood park, or local trails, every observation contributes to real ecological data.

• Observation Dates: April 24 - 27, take photos or record sounds of wild species
• Identification Period: April 28 - May 10, upload observations and help others identify species
• Results: May 13, final global results with be revealed

Open to all ages and experience levels and you can literally participate from anywhere! Learn more and get involved at www.citynaturechallenge.org/.

LAKE OSWEGO PUBLIC LIBRARY
Celebrate Arbor Month with a book! Throughout April, the Lake Oswego Public Library, located at 706 4^th Street, will have tree-themed books on display and Arbor Month Art Contest entries will be on electronic display from mid-April through mid-May. Open daily: 1 to 5 p.m. Sunday, 10 a.m. to 7 p.m. Monday-Thursday, and 10 a.m. to 5 p.m. Friday-Saturday.

GNOMES & BEES IN NATURE
Our forest friends are back! The wily Stewardship Gnomes, Blossom, Greenie and Oak, and their bee buddy, Polli will be hiding in natural area parks from April to September, moving to different parks on the first of each month. Come out and find them, you may win a prize! Here’s what to do:

• Find the forest friends in three different natural area parks each month. In April, they will be hiding in Hallinan Woods, George Rogers Park, and Pennington Park.
• Scan the QR code and take a photo of you, your dog, or anything else by a forest friend.
• With your participation, you may be selected to win a prize in October.

Visit lo-stewardship.org each month to learn where the Gnomes and Polli have moved and discover fun facts about native plants, wildlife, and the City’s 500-acres of park natural areas.

FREEPONS PARK COMMUNITY SURVEY DAY
Saturday, May 2, 10 a.m. to 1 p.m.
The Oswego Lake Watershed Council invites all past and present volunteers back to the field for a massive, high-energy community survey and friendly competition. Participants will team up to collect inventory data for Oregon white oaks in Freepons Park. Who can find the biggest trunk diameter? Who can pot the widest canopy spread? Whether you are a seasoned pro or just finished your survey training, come out to help map these giants and enjoy lunch provided for the whole crew afterwards. Capacity is limited and registration is required. Visit www.oswegowatershed.org/volunteer-calendar/ for more information and to sign up and complete the required waiver form.    

Explore these related links:

• Arbor Month Art Contest
• Tree of the Week
• Stewardship Opportunities
• Workshop Series
• Forestry at the Farmers Market
• The BUZZ on Bumblebees 
• Heritage Trees 
• State of the Urban Forest 
• Tree Care and Maintenance