It’s a quiet invasion but the Capital Regional District wants homeowners to be diligent in identifying and properly disposing of the invasive species knotweed.
The bamboo-like plant – in particular the Japanese, bohemian and giant varieties – is causing problems for waterways and other species of plants.
The plant, originally from Asia, is edible and has some medicinal properties. But it is listed by many countries as one of the worst invasive species. In B.C., knotweed is considered a priority for eradication.
“It’s a real vigorous one,” said City of Colwood parks manager Gordon Beauvillier, who is a member of the Captial Region Invasive Species Partnership (CRISP).
Last year, CRD parks workers tackled a patch on the Galloping Goose trail near Colwood Corners that had spread to about a six- to nine-metre square patch.
The biggest problems, said Beauvillier, are when residents grow the invasive species as an ornamental plant or simply don’t remove it properly.
“The stock and everything is very bamboo looking, it comes out with a nice, white flower,” Beauvillier said. “Once you know what it is, it’s hard to confuse it with other things.”
The plant has hollow stems that can grow three to five metres tall. The leaves are heart-shaped and come to a pointed tip. In late summer, the plant flowers with small white clusters.
Despite its good looks, however, knotweed can cause serious problems.
“It absolutely takes over waterway ecosystems,” Beauvillier said. “It will destroy waterways, which will destroy the wildlife and the fish habitat. It’ll clog waterways. It’s really bad. And it grows. It’s a vigorous grower and it’s extremely hard to get rid of.”
Disposal is at the heart of the problem. Knotweed is a tough plant. Beauvillier said there have been cases of the plants growing in landfills and it has also been known to grow through asphalt and concrete foundations.
For now, knotweed has mainly been kept to isolated patches on private properties. Some property owners are tackling the plant on their own, but Beauvillier said the Coastal Invasive Plant Committee, in partnership with CRISP, can help deal with infestations.
Knotweed needs to be disposed of properly or else it will grow back and spread.
“It’s the lack of information out there for people and the understanding of how bad it actually is that is really giving us a tough time,” Beauvillier said.
To report knotweed, call CRISP at 250-857-2472. For more information on the plant, visit www.coastalinvasiveplants.com.
Did you know?
• The Coastal Invasive Plant Committee classifies the various species of knotweed as species to be “contained,” meaning there are established infestations in the region that need to be contained before they spread.
Other plants in this category include diffuse knapweed, carpet burweed, yellow flag iris and butterfly bush.
• The next category, “control,” is for species with widespread infestations.
• Plants in this category are typically only fought if they are threatening a conservation area. Included in this category are burdock species, English ivy, St. John’s wart, tansy ragwort, Himalayan blackberry and Scotch broom.