Invasive plants targeted as Gee Creek’s banks undergo another round of weeding

By Marissa Harshman, Columbian Health Reporter

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Another piece of the city of Ridgefield’s multiyear effort to eradicate invasive nonnative plants along Gee Creek was recently completed.

The city received a $10,000 Department of Ecology grant in 2009. City employees, AmeriCorps teams and volunteers recently completed the work funded by the grant, which included replacing nonnative plants with 150 native trees.

“The people are very cognizant of the water around them and the wildlife around them,” said Mayor Ron Onslow. “Wildlife is important to people here. They want to keep that quality up. They want the wildlife to be safe. So they’re willing to step up and do it.”

The city began the effort in 2005 with a $12,500 grant from the National Fish and Wildlife Foundation. The recent grant, coupled with about $30,000 in city funds, allowed the city to continue the eradication efforts, said Public Works Director Steve Wall.

“There’s been a concerted effort for quite a few years, and I think they’re gaining on it, which is nice,” Onslow said.

Volunteer groups, led by city employees, worked to clear invasive Himalayan blackberry and English ivy plants from the area bordering Gee Creek.

A shot in the stem

Volunteers also marked large Japanese knotweed plants for eradication with herbicide, Wall said.

The city used some of the grant money to hire an AmeriCorps team to inject herbicide into the knotweed, he said. AmeriCorps teams used a device that looks like a gun with a long needle to inject herbicide into the stems of the plants, Wall said. The herbicide injection is the most effective way of removing the plant, he said.

The city first observed the Japanese knotweed along Gee Creek near the upper end of Abrams Park. Japanese knotweed can grow up to 7 feet tall in a single season. The plant then spreads, forming a thick, dense cover that crowds out other plants. The knotweed also has an extensive root system that can damage foundations, buildings, roads and retaining walls, according to the city.

“It really makes a difference in the quality of the creek and the banks surrounding it,” Onslow said. “If you let the blackberry or the knotweed go, they will fully take over and clog it up. It will give you terrible water quality.”

The city will likely continue its enhancement efforts in years to come in order to keep the plant from returning, Wall said.

“We need to keep a handle on the knotweed,” he said. “It never completely goes away.”

Once the invasive species were removed, volunteers planted native species such as red cedar and red osier dogwood in the open spaces. The new plantings will help stabilize the banks of the creek, Wall said.

In addition to the enhancement efforts, Wall said community education about the invasive plants is also important. Many people are unaware that the blackberry and ivy plants are nonnative and can cause problems along stream corridors. Wall hopes to incorporate education and outreach into future efforts.

Marissa Harshman: 360-735-4546 or marissa.harshman@columbian.com.