Squak Mountain Forest Restoration

21500 Southeast May Valley Road, Issaquah, WA, 98027

The Issaquah Alps Trails Club (IATC) and Washington State Parks are working together to restore native forest habitat on Squak Mountain by removing invasive English holly. Led by IATC Forest Stewards Anne Newcomb and Nicole Deflaux, alongside Washington State Parks Ranger Ellen Moline, this ongoing project brings volunteers together to protect the health and biodiversity of our local forests.

Why Remove English Holly?

English holly (Ilex aquifolium) is a Class C noxious weed in Washington State. Its dense growth shades out native understory plants, and it can release chemicals that harm nearby vegetation. Holly is also highly flammable and can potentially increase wildfire risk. It's difficult to eradicate once established. Cutting down a mature tree often triggers vigorous regrowth, and holly can spread through seeds and new shoots. Left unchecked, it can expand through forested areas and displace native vegetation.

Our Restoration Approach

Since March 2024, volunteers have contributed 660 hours to addressing 118 groves of holly on Squak Mountain. Larger trees are treated with a targeted herbicide injection to prevent regrowth, while smaller saplings and shoots are pulled by their roots. This approach helps control the spread of holly and gives native plants more room and resources to recover. Though the work takes patience and continued effort, each treated grove is a step toward a healthier forest.

Invasive Holly Removal Method

European holly is a persistent invasive species that can shade out native understory plants and release chemicals that may harm nearby vegetation. Because cutting mature holly trees often triggers vigorous regrowth from the stump, effective removal requires a targeted approach. On Squak Mountain, volunteers inject larger holly trees with herbicide and manually pull smaller saplings and new shoots, including their roots, to prevent regrowth. This method helps control the spread of holly while allowing native vegetation to recover and supporting the long-term health and biodiversity of the forest.

Additional learning resources

• Sugi Project What Miyawaki Method

• Miyawaki Forests: Building Community with Native Plants

• Afforest Tiny Forest Handbook PDF

• Why We Need Urban Biodiversity

Why Remove English Holly?

English holly (Ilex aquifolium) is an invasive, Class C noxious weed in Washington State. It forms dense growth that shades out native understory plants and can release chemicals that harm nearby vegetation. Because cut trees can resprout, effective removal takes ongoing effort. By removing holly and preventing its spread, volunteers are helping native plants recover and restoring the health and biodiversity of Squak Mountain’s forest.

Additional Learning Resources

• Washington State Noxious Weed Control Board  — Learn about noxious weed classifications and management.

• King County Noxious Weed Control Program  — Explore invasive plant identification and control resources.

• Washington State Parks  — Learn more about state park stewardship and natural resource management.

Other Local Restoration Projects

Explore other efforts to protect and restore native habitats in the Issaquah Alps and surrounding communities:

• Issaquah Miyawaki Forest

• Green Issaquah

• Issaquah Alps Trails Club  restoration events and volunteer opportunities