Knotweed: a menace in disguise

Unless you’d heard about it beforehand, you would never know how dangerous Japanese Knotweed is just by looking at it.

Unless you’d heard about it beforehand, you would never know how dangerous Japanese Knotweed is just by looking at it. It’s not spiky, it’s not menacing, and it’s not poisonous. It resembles bamboo but for its broad, heart-shaped leaves. It seems completely innocent; just another plant minding its own business, enjoying sunlight and all that good stuff. Nothing to see here, move along.

Much like Clark Kent, looks can be deceiving. Unlike Clark Kent, Japanese Knotweed is not a blessing in disguise — it’s an ecological terror, laying waste to whatever stands in its way. The plant can grow through concrete roadways and brick walls. It can take over fertile areas to the point of creating a monoculture — an area completely made up only if its own species. It’s even been known to divert rivers. Not only that, it’s also extremely difficult to get rid of. Ripping it out won’t work. Digging it out won’t work. The plant has roots that can reach 20 meters horizontally and 3 meters deep. Even burning the plant doesn’t solve things; any tiny bit of knotweed that remains can and will sprout into a new shoot. These reasons are why it’s ranked as #37 of the most invasive species worldwide.

Japanese Knotweed hasn’t stayed in Japan. Brought to England in 1850 and originally discovered by an explorer by the name of Philipp von Siebold, it quickly became popular for its pleasing looks and easy-to-grow nature. Now, it’s a national epidemic in Britain; one that can destroy property values, cost thousands of dollars in legal fees, and even cause lenders to deny mortgages. Without a single 15,000 hectare patch of land in all of Britain without the plant, such extreme reactions are understandable.

Japanese Knotweed has spread across Canada, even to isolated places like Nakusp. This Superman plant does have a Kryptonite, but it is incredibly tedious to administer. The plant must be dosed with a herbicide, which is either injected into or sprayed onto every individual stalk. If any stalks are missed, the plant can recover. In a best-case scenario, the infestation will be gone within the season; more than likely though, it will take longer than that to completely eradicate.

Researchers have been delving into the knotweed problem with three herbicide-free alternatives having shown success; one using saltwater sprayed over the plants, one using a psyllid that feedsexclusively on the plant, and another using a leaf spot fungus.

While the trials have been promising, there remains much testing to be done — after all, no one wants to introduce a new invasive species in an attempt to combat an old one. There are other available options for containing the weed’s spread, but for the moment, nothing less than chemical warfare can truly kill Japan’s Godzilla of weeds.

The village council is busy drafting up a plan to deal with the plant on public property, as well as an awareness campaign for private property owners. Until then, keep an eye out for the plant, and make note of its location if you do spot one. With knowledge, vigilance, and persistence, we should be able to prevent Japanese Knotweed from gaining any more of a roothold in our neck of the woods than it has already. If it’s a horticultural Superman, consider us Lex Luthor.