Trouble in Paradise—Invasive Plants

I see ivy (Hedera helix), a serious pest in the Pacific Northwest, growing on trees in many

Weyerhauser building covered in ivy. ©2006

locations in Washington, Oregon and British Columbia. Until I walked through Fort Ward State Park on Bainbridge Island, Washington, did I realize the full impact this species has on our forests. In this park, the ivy has invaded a large portion of forested areas. In most parts of the forested areas, the plant grows up the trees or along the ground; everything in its path is smothered in the glossy telltale leaves of ivy. It has destroyed the diversity of the native plant life on the forest floor. All that remains is a mono-crop vine that will soon destroy the trees. After seeing the carnage, imagine my surprise when I saw the Weyerhaeuser building in Federal Way, Washington, purposely planted with ivy, the very plant that threatens the forests that their business depends on.

In May, when our northwest native Rhododendron macrophyllum is in bloom, I love driving through Whidbey Island or around the Kitsap Peninsula, spotting the vast amount of this native species in full regalia. On a coastal trail near Florence, Oregon, one May I went for a hike just to see these rhododendrons in bloom. The last few summers I noticed the invasive scotch broom (Cytisus scoparius), with its electric-orange flowers, bloomed at the same time as the rhododendron’s trusses of soft pink flowers opened. The scotch broom’s color overpowered everything. If the pink flowers grew close, the garish orange flowers clashed; growing further away, the rhododendron flowers faded into the woods. Besides the scotch broom being unappealing, it reseeds itself prolifically and out competes our native plants.

These are just a few examples of plants gone wild in our region. A smorgasbord of exotic and native plant species are available to gardeners from nurseries, but only a handful of plants are invasive. As gardeners, it behooves us to avoid planting the species that have a tendency to take over our gardens as well as our natural areas. Already too many species have escaped from the genie bottle, and we are paying the price! Since we have so many alternative plants, we can remove or avoid planting invasive species that add to the problem, such as the rangy butterfly shrub (Buddleia davidii). Instead, look for alternatives filling the same niche. In this case a spirea is an attractive alternative which feeds the butterflies and adds beauty to our landscapes.

A free booklet, Garden Wise, Non-Invasive Plants for Your Garden is available online to download. Some invasive plants included in this booklet may surprise you. Listings include troublesome plants from butterfly bush (Buddleia davidii) to policeman’s helmet (Impatiens glandulifera). Alternative non-invasive plants to use instead are included.

Rainy Side Gardeners brings a list of invasive plants with tips on removal and a selection of suitable alternatives, including native as well as exotic plants that won’t destroy our beautiful forests, wetlands and prairies.

Debra Teachout-Teashon
Photographed at Weyerhauser, Federal Way, Washington.

Tell a friend about this page!

Questions, comments or suggestions? Would you like to communicate with other Pacific Northwest gardeners? Please join us on our forum.

Back to Pest Watch Index