Most people are familiar with the alien plant Scotch broom, but fewer know about the much more threatening species knotweed.
These aggressive 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 next 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 hand-pulling 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 Nunn’s 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.”
Milligan adds, “Other estuaries have been significantly impacted by knotweed, which erodes banks and damages salmon habitat.”
This year, Greenways volunteers made a fantastic impact by removing Scotch broom and yellow flag iris from our stream corridors, but when it comes to knotweed, professionals are required.
Some of the project funding was provided by BC Hydro ($5,000) and Fisheries and Oceans Canada ($1,000).
Knotweed was treated in Nunns Creek Park and Simms Creek watersheds, the Seawalk and along the Myrt Thompson Trail.
Greenways also plans 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 our natural places. One inadvertent wheelbarrow full of knotweed can mean years of costly treatments to regain the environmental health of our salmon habitats. Prevention is absolutely the most important action to avoid this “biological pollution.”
To report an infestation, visit www.reportaweed.ca or call Greenways at 250-287-3785. E-mail greenways@greenwaystrust.ca