NORTH BEND – There may be enough invasive plant species in the Valley to literally choke a horse.

Though they appear to be harmless foliage, viny villains, such as the Japanese knotweed, can out-shade native vegetation, yet do not provide adequate shading or food for wildlife and aid erosion.

The city of North Bend and the Mountains to Sound Greenway Trust are cracking down on invasive species near Ribary Creek with $65,000 in grants from the King County Rural Community Partnership Program and the King Conservation District.

Ribary Creek passes through the historic Tollgate Farm between North Bend and Snoqualmie. The farm became public property of North Bend and King County in 2001, but for many years was a dairy farm and in the 1880s served as the western toll collection site for the Snoqualmie Pass Wagon Road.

Ecologists want to save the area and two others in the Valley from the undesirable effects of invasive species. Knotweed and non-native blackberry plants are the two major culprits.

Mountains to Sound is currently in the process of acquiring a permit from North Bend to start work that will involve mowing down the culprits on 1.5 acres of the farm along 1,000 feet of Ribary Creek, removing them, treating the affected areas and planting native trees and shrubs. The project will also include fencing off one part of the farm, which is still used for cattle, to ensure the animals don’t munch on the new plantings. The area will have to be maintained for two years to make sure the other plants don’t grow back. If Mountains to Sound receives its permit soon, work on Ribary Creek would begin this fall.

Tor MacIlroy, director of field programs at Mountains to Sound, said 20 different kinds of native species including western red cedar, Douglas fir, willow trees and many different shrubs will be planted in place of the invaders. Volunteers will be needed to come out and help plant several thousand potted trees and shrubs.

Mountains to Sound is working on two other projects in the Upper Valley this fall, as well. Invasive plants on Gardner Creek near the Meadowbrook Farm Interpretive Center will get the boot, and many native plants and trees will be planted there, too. Mountains to Sound is also working with the city of Snoqualmie to do similar work near Kimball Creek.

One problem with invasive species is their inability to shade water.

“You want to keep the water cool as it travels to the Snoqualmie and Snohomish rivers and out to Puget Sound in Everett. Some [native] shrubs provide much better habitat and food for wildlife,” MacIlroy said.

Elk and a multitude of birds call Tollgate Farm home. A bald eagle’s nest has even been rumored to be located in the area. Native animals have evolved to be dependent on native plant food sources. Invasive plants harm wildlife by choking out their natural food supply. Most invasive plants don’t provide any nutritional value.

“[Invasive species] will out- compete everything else and be the only species living there. Japanese knotweed is more like bamboo; it takes over stream banks and nothing else can grow there. It’s kind of like bringing in a T-rex,” MacIlroy said.

Some invasive pests spiraling through Western Washington include blackberry plants, butterfly bush, fennel, purple loosestrife, Himalayan blackberry, evergreen blackberry, English ivy and English holly, among others. English ivy, MacIlroy noted, can crawl up a 200-foot tree and choke it out–killing it.

Invasive species can get into countries where they are not welcome in a few different ways. Some people who appreciate their scrappy looks bring them over and plant them in gardens where they eventually take off and creep elsewhere. Animals also carry them about, gnawing on blackberries and dropping the seeds; other plants are carried in by ships.

“We’re becoming more and more aware of invasive species all the time,” MacIlroy said. “The forest service determined they are one of the top three threats to our native species.”

Those interested in helping with any of the projects are asked to contact Kelly Kirkland at Mountains to Sound by calling (206) 812-0122 or e-mailing volunteer@mtsgreenway.org.

* For a list of invasive species and other information on dangerous or unwanted plants, visit the King County Noxious Weed Program at http://dnr.metrokc.gov/wlr/lands/weeds.

Staff writer Melissa Kruse can be contacted at (425) 888-2311 or by e-mail at melissa.kruse@valleyrecord.com.