British Columbia

'The monster is underneath': Interior district steps up fight against Japanese knotweed invasion

The green, heart-shaped leaves and bamboo-like stalks of Japanese knotweed may look pretty, but it can badly damage buildings and ecosystems — and now the Thompson-Nicola Regional District is stepping up its fight to root out the plants.

Roots of the invasive species can extend 20 metres underground and penetrate home foundations

'[Their] roots can extend 20 metres laterally and they're really, really strong and they can actually penetrate through concrete, asphalt [and] home foundations,' said Colleen Hougen, invasive plant management co-ordinator for the district, describing Japanese knotweed. (Jenifer Norwell/CBC)

The green, heart-shaped leaves and bamboo-like stalks of Japanese knotweed may look pretty, but it can badly damage buildings and ecosystems — and now the Thompson-Nicola Regional District is stepping up its fight to root out the plants.

Japanese knotweed is listed by the International Union for Conservation of Nature as one of the 100 worst invasive species, and sightings of it has the district in B.C.'s southern Interior concerned. 

"It doesn't look so scary up top but the monster is underneath, under the ground with its roots," said Colleen Hougen, invasive plant management coordinator for the district. 

The Thompson-Nicola Invasive Plant Management Committee is now asking the public to report sightings of the plant so they can try to develop a strategy to manage Japanese knotwood throughout the region.

People often buy the invasive plant because they think it looks pretty, but they don't realize how it can damage the infrastructure surrounding them, said Hougen. (Jenifer Norwell/CBC)

The plant can cause serious damage to buildings and infrastructure, Hougen said.

"[Their] roots can extend 20 metres laterally and they're really, really strong and they can actually penetrate through concrete, asphalt [and] home foundations," said Hougen.

The weed tends to grow in wet areas and if it grows on a river bank, it can cause erosion and sedimentation, which can effect aquatic ecosystems, she added.

'Growing through people's homes'

Japanese knotweed is not new to the region, but the district is trying to get a handle on the weed "before they get out of control," Hougen told Daybreak Kamloops' Jenifer Norwell.

"Out of control could look like root systems growing through people's homes and showing up on the insides of their homes."

The plant is much more prevalent in the Lower Mainland and along the coast because of the wet climate, she said.

However, people in the Interior still plant it and nurseries sell it.

"It's really unique and people are drawn to that for their gardens," said Hougen. "What they don't know is the impacts that the roots can have to the infrastructure surrounding them."

Call district or specialist for removal

The district does not recommend people remove the plant on their own, because it can easily reproduce through root fragments and shoots.

"Pulling and digging will actually make it worse," said Hougen.

Instead, the district asks people to contact them or a specialist to try and help remove it. A common treatment option is using herbicides.

So far, the district has just started outreach with landowners who have Japanese knotweed on their properties, and it has already had one success story with a hotel in Clearwater.

"I feel if we team up with some landowners and land managers and if we work together we can actually make headway, and kind of control these plants before they get out of control."

Japanese knotweed is a beautiful looking plant, but it's one of the worst invasive species in the world. Colleen Hougen with the Thompson Nicola Regional District explains why it's so bad, and how to get rid of it. 5:09

With files from Jenifer Norwell and Daybreak Kamloops

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