Knotweed in Macleans
Have you read the new article about knotweed in BC in Macleans?
'The plant that's eating BC' by Ken MacQueen
Councillors ordered a staff report, and Cindrich returned to his lonely war against a dense thicket of knotweed that had grown to 1,800 sq. m and clearly had territorial ambitions. It was on a neighbouring property belonging to a widow. “She thought it was beautiful bamboo,” though she had no idea how it had gotten there. By now, Cindrich had revised his tactics. A frontal assault with pick and shovel only seemed to make it grow faster. He opted for chemical warfare, settling on a 12- to 15 per cent solution of the herbicide Roundup injected into each individual stalk: maybe 10 seconds per stalk; stalks by the tens of thousands; hours by the hundreds. He was a one-man conscript in a war of attrition. He’d be out most mornings, mixing his chemicals, wielding his injection machine, as relentless as a knotweed. It is the hobby from hell. “But,” he says, “what is the alternative?”
The alternative, in fact, is chaos. It has crept on cat’s feet into all provinces with the likely exceptions—so far—of Manitoba and Saskatchewan, says Gail Wallin, executive director of the Invasive Species Council of B.C., and co-chair of the Canadian Council on Invasive Species. The spread is helped, some studies suggest, by climate changes that have extended its range. It is changing river flows, choking spawning beds, undermining riverbanks, shorelines and hillsides, punching through roadways and threatening the foundations of homes.
How scary is this plant? When engineers found it growing beside the massive concrete footings of Vancouver’s Lions Gate and Ironworkers Memorial Second Narrows bridges, it was deemed a safety threat requiring lethal chemical intervention. “The ministry of transportation takes knotweed extremely seriously,” says Jennifer Grenz, program manager for the Invasive Species Council of Metro Vancouver. “They are very aggressive in their treatments, because of the threats to infrastructure. We’ve had examples of plants we’re pretty sure have gone under four lanes of highway and have popped up on the other side.”
When a huge infestation of Japanese knotweed was discovered at the coastal Mission Point Park in the Sunshine Coast community of Davis Bay, B.C., crews from the District of Sechelt attempted a chemical-free strategy. They moved in with an excavator and dug out the plants to a depth of about three metres. The next year, parks supervisor Perry Schmidt would later report, the knotweed doubled in size.
The threat level is so high that Wallin and her national co-chair, Barry Gibbs, are pushing to relax varying provincial limits on using herbicides close to waterways. In B.C., for example, herbicide use is prohibited within one metre of a shore, creating “havens” of knotweed, says Gibbs, executive director of the Alberta Invasive Species Council. Mechanical means such as digging and pulling risk sending plant fragments adrift to colonize elsewhere. “When you’re thinking of using a herbicide like glyphosate [usually sold as Roundup], you have to look at the risk of not doing it,” says Gibbs. There is a need to hit the weed hard, with early identification of infestations, tougher regulations, and chemistry, “before it’s like the U.K., where it’s essentially an epidemic,” says Gibbs.
Britain does indeed have it worst. A single stalk of knotweed found on a property, or even on a neighbour’s lot, devastates a house’s value and makes it near impossible to obtain a mortgage or insurance. It has led to financial ruin, depression, even a murder-suicide. A botched attempt to remove the weed may only drive it underground, where it can remain dormant for a decade or more. “Once the coast is clear, once you’ve built your nice, new conservatory, up it pops again,” notes a Sunday Times magazine cover story, “The plant that ate Britain.” The article continues: “The trick is to poison it slowly, subtly, so it won’t notice, like an Agatha Christie nun slipping drops of arsenic into the vicar’s nightly bowl of soup. The process can take up to five years.”
A knotweed plant arrived in England in 1850 and was added to the collection at the Royal Botanic Gardens at Kew on the fringes of London. It was a specimen from a plant, plucked by European adventurer Philipp von Siebold some years earlier, from the rugged slopes of a Japanese volcano and transported to Holland. It became a darling of U.K. gardeners and landscapers (and, later, those in Canada), who loved its tall, dense stands of bamboo-like stalks, its lush leaves, white flowers and ease of growth. Growing was never the problem. The slightest fragment of root or stalk dropped on disturbed ground will colonize. It advances as much as eight centimetres a day, and can reach five metres in height or more. It is hardy. Subsurface, its roots can extend three metres or more deep, and 20 m across, in a constant search for water and the tiniest cracks or seams in barriers blocking its quest for light. Just over a century and a half after the plant arrived in Kew, there is not a single 1,500-ha patch of ground in the entire U.K. that is not rooted with at least one Japanese knotweed, all perfect DNA clones of von Siebold’s disastrous legacy.
The U.K. government estimates that the cost of controlling knotweed has hit the equivalent of $3 billion. In just one epic example, organizers for London’s 2012 Olympic Games had to eliminate a knotweed infestation on a patch of east London land on the proposed site of the velodrome and aquatic centre. In some areas, rendering it safe required a three-year herbicide assault on the plants. Where construction schedules required a faster solution, the plants were rooted out by deep excavation and dosed with herbicide, then roots and stalks were screened from the dirt and incinerated. Knotweed-contaminated soil was then buried to a depth of five metres, after it was encased in a “proprietary knotweed root membrane.” A further two metres of clean fill was added on top, carefully sorted of sharp objects that might cause a tear and allow a knotweed shoot to arise from its sarcophagus. Vampires don’t merit that much respect. Total cost: the equivalent of about $130 million.
But it is Brits without deep pockets who have it worst. An estimated 220,000 homes are infested, fertile ground for a lucrative new branch of the legal industry. Reports abound of it ripping through foundations, infesting floor and wall cavities and poking out of baseboards and electrical sockets. A single stalk in a back garden killed a house sale for a woman called Mary, the Sunday Times reported. The culprit, a neighbouring care home, had to spend about $35,000 to remove the plant after it was threatened with a lawsuit. Mary eventually found a buyer, but at a substantial loss. Another homeowner, Sarah, was in a legal battle with a neighbour, who refused to remove the weed from her own garden. Because Sarah’s property was under siege, her lender was threatening to cancel her mortgage. Perhaps the saddest case, though one obviously clouded by mental illness, was triggered by the discovery (mistaken, it would later turn out) of knotweed in the garden of Kenneth McRae. “I believe I was not an evil man,” he wrote, “until the balance of my mind was disturbed by the fact that there is a patch of Japanese knotweed, which has been growing over our boundary fence on the Rowley Regis golf course.” The note was read at a coroner’s inquest after he battered his wife to death with a perfume bottle before killing himself.
Awareness of the potential problem in Canada has dawned more slowly. In the U.K., those caught selling or dumping knotweed are subject to fines, or up to two years in jail. In Canada, it is only in recent years that most knowledgeable garden centres have stopped selling knotweed. Even now, knotweed sometimes slips into inventories of weekend plant swaps, or even big-box garden centres, where it is sold as “false bamboo,” says Wallin. Adding to its falsely benign image is the fact that spring shoots of knotweed are edible, sort of a cross between asparagus and rhubarb. Internet recipes abound for things such as strawberry knotweed pie, knotweed muffins, even knotweed wine. Don’t go there, says Wallin.
In Vancouver, crews have just finished treating outbreaks of knotweed throughout Stanley Park. They wisely posted explanatory signs telling why the infestation merits the exceptional use of herbicides in the iconic site. Even so, spray crews are sometimes castigated by those objecting to herbicide use, says Grenz of the Vancouver invasive-species council. “We’re an environmental non-profit . . . and we don’t take it lightly. We’re being accused of all kinds of things: that we work for chemical companies and we have some other kind of agenda. But we’ve seen first-hand what it does,” she says of the weed. “We’re trying to use these tools to stop major catastrophes with infrastructure, to keep people safe and allow there to be salmon habitat.”
There have been many successes. “We’ve been at this for a solid five growing seasons, and can comfortably say we’ve eradicated it from a number of areas,” says Grenz. “Without having to do any restoration work, we’re seeing the native species return on their own.”
Unfortunately, that progress comes with a caveat. Rather like the marauding killer plants in the sci-fi classic Day of the Triffids, knotweed is not the surrendering type. In Canada, especially B.C., a mutant hybrid has developed, a cross between Japanese and giant knotweed known as Bohemian knotweed, which now accounts for about 80 per cent of infestations, by one estimate. “The monster we thought we had, which is what happened in the U.K., is turning out to be our own sort of unique monster,” says Grenz, “presenting even more issues.”
Whereas Japanese and giant knotweed spread only by root and stem fragments, and usually at predictable rates, Bohemian knotweed is a runaway train. “All of a sudden, we were noticing that knotweed was popping up everywhere. You’d look at one patch one year and then, next year, it’s more than doubled and we were trying to figure out what was going on,” says Grenz, who is doing graduate work on the hybrid at the University of British Columbia. “It was ending up in really bizarre locations, where it wasn’t possible for anyone to have moved any. What we discovered is that the seeds are actually quite viable, and they’re prolific seed producers. On one branch, you’re looking at 100,000 seeds.”
With that come a host of questions. How long are seeds viable in the soil? Can birds spread them? Will the genetic variability that results from seed production, as opposed to the cloned reproduction of Japanese knotweed, eventually result in a herbicide-resistant strain? Grenz asks. “It just puts a new urgency on us to quickly, swiftly be dealing with this, or forever be chasing our tails and losing valuable habitat.”
When Joe Cindrich drives the highways and back roads of the Fraser Valley these days, he sees much evidence of spray and injection attacks on his old foe. He’d like to think he helped to raise the alarm. His neighbour’s crop is now largely obliterated. A few new plants pop up, but Cindrich never lets them get beyond a foot high before he doses them with extreme prejudice.
Meantime, in the U.K., and now, B.C., combatants are testing a new weapon in their slim arsenal. It’s a tiny sap-sucking bug called a psyllid, a Japanese predator that appears to feed exclusively on knotweed. The bugs have been introduced under strict controls to several sites in the U.K. There are also a few psyllid trial sites in B.C., Wallin confirms. That said, don’t expect Canada to be importing an army of the “little critters” any time soon, she says. “There is a lot of science that goes into it before it is determined if the biocontrol is a safe one for use in B.C. and in Canada.”
No one wants to be remembered as the next von Siebold, the one who introduces a promising new species, with catastrophic results.