Saturday, September 8, 2012

Japanese knotweed poses public safety threat: ‘False bamboo’ can crack concrete, including bridge foundations and roads

It’s an invasive bamboo-like plant that splits concrete, grows through retaining walls, resists almost any attempt to kill it and can regenerate itself from just a tiny chunk of root.
Japanese knotweed is found throughout Metro Vancouver and was recently spotted at the base of the Ironworkers Memorial Bridge, leading an invasive plant specialist to recommend all bridges and overpasses in the region be assessed before the plant puts lives at risk by growing through — and weakening — concrete foundations.
“There’s not a full understanding of the damage the plant can do in this region,” said Jennifer Grenz, program manager at the Invasive Species Council of Metro Vancouver. “This is a plant that can grow through three metres of concrete.
“It outcompetes blackberry ... and anything that can outgrow blackberry — that’s a feat in itself.”
The plant has been found along the Burnaby portion of Highway 1 from Boundary Road to Canada Way. The area is undergoing construction as part of the $3.3-billion highway and Port Mann Bridge expansion, but project spokesman Greg Johnson said the weed has not delayed progress.
Each plant was injected with herbicide — the only proven eradication method — and once confirmed dead, the plants were either taken away and incinerated or buried three metres deep in the ground, Johnson said.
If left untreated the weed could seriously damage bridges and roads and even pipelines, Grenz warned.
“It’s finally come to a head where it is having an impact on infrastructure,” she said.
The plant has been known to choke off the banks of waterways from native plant species and grow through the foundations of houses, causing headaches for homeowners.
Residents who find the plant on their property should hire a landscaping company capable of destroying it with a herbicidal injection said Grenz, who owns an organic blueberry farm in Richmond and has seen the weed around her property.
Under the B.C. Weed Control Act, herbicides can be legally used on knotweed. However, Metro Vancouver lacks a coordinated strategy, like that of the Fraser Valley region, to deal with invasive plant species, Grenz said.
Vancouver Coun. Heather Deal, chairwoman of Metro Vancouver’s environment and parks committee, agreed the region needs a plan.
“You need to make sure people on both sides of the imaginary line between cities are doing the same work, because, as we know, invasives don’t recognize municipal boundaries,” Deal said.
Grenz asked Deal’s committee Wednesday for a $40,000 grant to coordinate a regional invasive plant strategy. Grenz said her council, which manages invasive species along local highways, could develop the strategy with another $35,000 grant from other levels of government.
Metro Vancouver staff will review the request and a decision will be made during the next committee meeting in September, Deal said.
Japanese knotweed, also called false bamboo, can grow more than two metres a year and was first exported from Japan as an ornamental plant that could provide fence-like cover and flourish with little care. The weed has also become a problem in the United Kingdom, where authorities faced massive cost overruns when they began construction of London’s Olympic Park velodrome in 2007 and found four hectares of the weed at the derelict site.
If removed from its soil, the weed can regenerate from a chunk of root weighing less than a gram, Grenz said. The plant composts very slowly and when mowed over, Japanese knotweed can produce a “million new plants,” she added.
“Plants aren’t as scary as the fish or insects that grab attention more quickly,” said Grenz of the weed’s inconspicuous infestation of the region. “It’s sad we’re at the point now where there’s so much damage that you can’t ignore it.”

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