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  • Jenna Cardoso

Restoring Little Lake Forest by Removing Invasive Holly

It's June and raining off and on at Little Lake. The team is removing holly (Ilex aquifolium), an invasive weed found in the understory of the 155-acre site in Enumclaw. The site comprises lowland forests, a lake, open fields, and a powerline corridor. When the rain breaks, I hear the song of the Swainson's thrush (Catharus ustulatus) echoing through the trees. Sophie (our expert birder) is the first to identify the song. She stops momentarily to listen and calls it "the sound of summer." My spirit lifts at the thought of summer even though it's cold and windy and it doesn't feel like summer at all as we remove this invasive Christmas plant from the forest.

Holly Threatens Forests in the Pacific Northwest

Holly was first introduced to Washington from Europe in the late 1800s. You can easily identify holly by its shiny, sharply toothed dark green leaves and red berries that fruit in winter. Towering between 20 and 50 feet high, holly crowds out surrounding native plants, outcompeting them for resources. In 2010, holly was classified as a Class C noxious weed in Washington. Class C weeds are managed via public education and local control efforts. The goal is to prevent their spread into new areas and manage them where they've already been established. 

The image shows holly with its shiny, dark green leaves and sharply toothed edges.
Holly with its shiny, dark green leaves and sharply toothed edges.

Managing Holly in the Little Lake Forest 

Noxious weeds can pose a significant threat to forests. If left unchecked, they can invade forest habitats and completely change the structure and chemistry of the forest. Some studies suggest that holly must be managed quickly, or it could become a dominant forest species in the Pacific Northwest. Removing and preventing holly from taking over this forest is critical for the native plants growing here, such as trailing blackberry (Rubus ursinus), black cap raspberry (Rubus occidentalis), and oso berry (Oemleria cerasiformis).

We're currently removing holly by pulling runners and smaller trees and injecting larger trees with herbicide. Holly runners are the stems that grow underground and aboveground to grow new plants. After we've pulled what we can, we inject the larger stems with specialized capsules filled with the herbicide imazapyr to kill holly plants, preventing future growth. This is the most effective method for treating holly and allows us to target specific plants, reducing herbicide use and limiting ecological risks. 

The image shows a person identifying holly stems to inject with herbicide capsules.
Our team lead, Brandon, identifying holly stems to inject with herbicide capsules.

Next Steps at the Little Lake Forest

The sun is peeking through the canopy as we finish the day, and it feels warmer. As we leave the site, I glance through the forest and see all the native plants freed from the deathly crowds of holly today. The Swainson’s thrush is singing again, and the forest feels more rejuvenated with each note. By removing the holly, the native species can now flourish this summer. We've been working here since March, first tackling the non-native blackberry and now holly. But, we still have work to do and will return later to continue this project because restoring a 155-acre forest takes time. However, the new life we see growing in place of the invasives is a sure sign that healing is happening.

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