English ivy invades Pacific Northwest forests

English ivy infestation in Olympic National Park
English ivy, like this infestation in Olympic National Park, can kill and pull down trees. Photo: Kevin Zobrist/WSU Extension.

What’s wrong with a little ivy? Plenty. The photo with this post was taken recently in Olympic National Park, demonstrating that invasive species know no boundaries. This was only a small piece of the infestation, which was killing and pulling over trees and completely destroying the native plants growing under the trees. This immense spread of ivy has very little value for wildlife, unless you’re a rat.

Native to Europe, English ivy and similar cultivars were introduced to North America by early settlers who prized it for ornamental purposes. It continues to be widely planted as an ornamental, according to the Invasive Plant Atlas of the United States. Because of its shallow, mat-like root system, ivy is a poor choice for controlling erosion, such as on hillsides.

“But I only have a little,” you say? That’s how this started out. English ivy spreads aggressively both vegetatively and by bird-disbursed seeds. There are a number of different varieties, all invasive and all brought in as ornamentals.

Getting rid of ivy

Spraying is challenging because ivy has a thick, waxy leaf, but there are some herbicides listed for use (always follow label instructions). Fortunately, English ivy pulls up (roots and all) pretty easily, so with a little elbow grease you can make good strides in eradicating it. You should wear gloves and a dust mask for this, for the sake of comfort. For ivy that is growing up and strangling trees, you don’t have to pull it all off the tree (which could damage the bark). Instead, pull the ivy off the tree up to shoulder height, making sure to sever all stems growing up the tree. Without ground contact, the remainder up the tree will die. Then work on pulling the stuff on the ground back from the tree, pulling it up by the roots. Here are two Pacific Northwest-oriented fact sheets about controlling English ivy:

Check out King County’s list of native plant alternatives to English ivy.

[This blog post was excerpted from an article in Forest Stewardship Notes by Kevin Zobrist, regional extension forestry specialist, WSU Extension Service. Forest Stewardship Notes is a free quarterly e-newsletter published jointly by DNR and WSU Extension Service. Sign up for a free subscription today.]