Knotweed infestation growing

02-08-2013
Most people are familiar with the alien plant Scotch Broom, but fewer know about the much more threatening species knotweed. These aggressive alien plants grow better in their new habitat due to the absence of native predators and diseases that limit their growth at home.

Japanese Knotweed is a tall shrub with bamboo like stems. Knotweed grows in many habitats, but is of most concern adjacent to streams and rivers.

"We are most concerned with the health of the Campbell River estuary, which is such an important salmon habitat," says Sandra Milligan, Greenways Vice President who spearheaded the first knotweed treatments along Myrt Thompson trail last year.

Knotweed's incredibly extensive root system and sprouting ability makes it extremely difficult to control. Digging or handpulling causes plants to send more roots underground and actually increases the infestation size. Herbicide treatments are the only known effective means of removal.

Ernie Sellentin, Invasive Plant Specialist from the Coastal Invasive Plant Committee, says, "We retreated over half of last year's 10 small knotweed infestations. First time treatments were applied to infestations along Homewood Road that threaten Nunns Creek and to infestation on Simms Creek and the Campbell River. We are very fortunate to have been able to attack these small infestations before they become much more costly to eradicate," said Sellentin.

Milligan says the problem is getting worse.

"Other estuaries have been significantly impacted by knotweed, which erodes banks and damages salmon habitat," she said. "Millions of dollars have been spent to revitalize estuaries in Washington State; the Cowichan River has over 100 infestations. We can't let that happen to our Heritage River or our salmon."

Greenways Volunteer Coordinator Cynthia Bendickson says that "our volunteers this year have made a fantastic impact by removing Scotch Broom and Yellow Flag Iris from our stream corridors, but when it comes to knotweed, we do need to call in the professionals."

Some of the project funding, with appreciation, was provided by BC Hydro ($5,000) and the Department of Fisheries and Oceans ($1,000). Knotweed was treated in Nunns Creek Park and Simms Creek watersheds, the Seawalk and along the Myrt Thompson Trail. Greenways Land Trust also invested as part of its long term plan to eradicate knotweed from streamside habitats.

"The most important piece of this work, however, is public education," says Milligan. "Most infestations result from land owners illegally dumping yard waste in natural places. One inadvertent wheelbarrow full of knotweed can mean years of costly treatments to regain the environmental health of salmon habitats. Prevention is absolutely the most important action to avoid this "biological pollution."

To report an infestation you can visit www.reportaweed. ca or please call Greenways Land Trust at 250-287-3785 or greenways@greenwaystrust.ca to ensure our staff is aware of infestations to allow for longterm planning.








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