CAMPBELL RIVER, B.C- There’s not enough room in this town for the two of them.
After working to eradicate the invasive species called scotch broom, the City of Campbell River and Greenways Land Trust are teaming up to treat infestations of another unwanted species.
According to a press release, knotweeds are among the top 10 invasive species for control in B.C. and one of the 100 worst around the globe, as identified by the International Union for Conservation of Nature.
Initially introduced in the 1800s from Asia as ornamental plants, they spread quickly and compromise biodiversity and ecosystem processes. All four species of knotweed (Bohemian, Giant, Himalayan and Japanese) have been found in gardens and natural areas in Campbell River:
In the release, the city said they have contracted an annual $5,000 knotweed treatment program to Greenways Land Trust.
Below are the city’s recommendations on identifying and dealing with the invasive plant, taken from the press release.
How to identify knotweeds
- Also known as false bamboo, they have hollow stems that stand upright with reddish-brown speckles and thin, papery sheaths.
- Small white-green flowers grow in showy, plume-like, branched clusters along the stem and leaf joints.
- Leaves are heart or triangle-shaped on all species except Himalayan, which is elongated and tapered. Giant knotweed leaves are generally twice the size of the other three species. A distinguishing feature of Japanese knotweed is the zigzag pattern of leaf arrangement along the plant’s arching stems.
- Stems grow one to five metres high at maturity.
What to do about knotweeds on private property
Knotweeds’ extensive underground stems (rhizomes) may be up to three metres deep and travel 20 metres from the plant. Even if most of the plant is dug out, fragments left behind can remain dormant for up to 20 years. A dedicated, multi-year, planned approach is required. Here are some options:
- Prevention – Do (k)not plant them. Planting knotweeds is an offense under the City’s Environmental Protection Bylaw. Grow native and regional plants. Gardeners and landscapers can find alternatives to knotweed in the Grow Me Insteadbooklet from the Invasive Species Council of BC, which offer five recommended non-invasive native or exotic plant alternatives to 26 of the province’s most unwanted plants.
- If you have knotweed on your property, please report it to Lydia Stratemann at Greenways Land Trust via email to [email protected]. Given the re-infestation threat posed by knotweed on private land, you may be able to have your patch treated through the City’s knotweed program, which is administered by Greenways Land Trust.
- Chemical control – herbicides are applied through a certified herbicide applicator. This may require three to five years of treatment. Current research suggests this is the most cost-effective and successful form of treatment.
- Mechanical control – only applied under specific circumstances on small patches and may include repeated cutting over years.
Notes on disposal
Remnants of knotweeds require careful handling. Compost or dispose of chemically treated plants through curbside yard waste collection or at the drop-off centre. Bag and take untreated cuttings or seeds to the Campbell River Waste Management Centre (landfill) to dispose at a reduced tipping fee ($65 per metric tonne).
Report large infestations of knotweeds on private land to the City by emailing [email protected].”
