Concrete-breaking Japanese knotweed sprouting in Alberta

A plant that can crumble walls and break through concrete foundation is starting to put down roots in Alberta.

'I've seen it go under roads and come up through the pavement,' says invasive plant expert

The invasive plant can crumble walls and break through concrete foundations, driving down property value. (Japanese Knotweed Solutions and inspectinginvaders.blogspot.ca)

A plant that can crumble walls and break through concrete foundation is starting to put down roots in Alberta. 

According to the Alberta Invasive Species Council, Japanese knotweed was spotted three times this spring — once in Leduc and twice in Calgary. In the past, it's also been identified in five other areas of the province:

  • Grand Prairie 
  • Parkland County
  • Sylvan Lake
  • Trochu
  • Waterton

'​Tip of the iceberg'

That may not seem like too much to handle, but the executive director of the Alberta Invasive Species Council says it's not a good sign.

I've seen it go under roads and come up through the pavement.- Barry Gibbs, Alberta Invasive Species Council

"It's usually the tip of the iceberg," said Barry Gibbs. 

"Usually, the ones we know about are only a small proportion of the ones that are actually out there," he said.

Gibbs, who is also the co-chair of the Canadian Council on Invasive Species, says unlike Japan, the country it originated in, Japanese knotweed has no natural predators in Canada.

Japanese knotweed can undermine river banks and home foundations. (CBC)

He says it has a "powerful" and "far reaching" root system that can grow three metres deep and up to seven metres away from the plant.

"I've seen it go under roads and come up through the pavement."

In Britain, Japanese knotweed has been wreaking havoc for years and can actually bring down property values.

"What occurs is the person trying to sell the property has no knotweed on their property but it's growing from an adjoining property into theirs," said Mark Haywood, with Britain's National Association of Estate Agents told CBC Radio's The Current

"They can't sell their property and may approach the neighbour to help pay for it to be eradicated," he said. 

Eradicating the dreaded weed

"It shouldn't be dug up. That's the worst thing you can do," said Gibbs.

That's because the roots multiply when you rip them out of the ground. 

The executive director of the Alberta Invasive Species Council says Japanese knotweed was likely introduced to Canada by gardeners. (Supplied)

Gibbs says if you think you have Japanese knotweed in your yard or garden, don't try dealing with it on your own — call in a professional.  

"The most effective thing we've found right now is to use herbicide and it's injected into the stem and it requires specialized equipment that most people don't have."

Gibbs says you should also notify the City of Calgary through 311 if you spot the invasive species anywhere in the city.​

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