Knotweed . . . don’t laugh

Sept. 7, 2017

Japanese plant already destroying public works budgets

American public works directors . . . lipsmoving . . . prepare . . . lipsmovinglipsmovinglipsmoving . . . to meet . . . lipsmovinglipsmoving . . . your doom.

The Japanese knotweed is not something fictionalized by Rising Sun cinema, but if Godzilla were real it would be a series of bamboo stems with leaves shooting out of its sides. Do you think I’m kidding? If you could see my face right now it would resemble a Bruce Lee death stare.

The Japanese knotweed has already launched a surprise attack in the United Kingdom, and it is still carpet-bombing the English landscape. Still not taking me seriously? It’s just the uppity Brits, right? Well, they are spending over $212 million a year trying to control perhaps the most destructive of unwanted plants in the history of the world. It breaks through pavement like it was penetrating through that Japanese glass made out of paper. Do not pretend you don’t know what I am talking about. We all saw Karate Kid II.

Originally used for fencing and sound barrier, Japanese knotweed can grow up to 15 ft tall, but the root is where you can find its death grip. The root can be 65 ft wide in all directions and as deep as 10 ft. You can find the weed growing in the sides of volcanoes. That’s right, lava as hot as 1,000° does not deter this green zombie. The leaves will burn, but the root stays alive and waits for a break . . . a single crack. This is why knotweed is an enemy of asphalt and concrete pavement, particularly in alleyways. It is such a problem in Kalamazoo, Mich., they now have a botanist tracking its every move; the plant professor has been hired for the sole purpose of trying to get this pest under control. For public works officials, it can be an uphill battle on the most active volcano on the planet, with Godzilla throwing fireballs at you.

Still chuckling? OK, well soil contaminated by knotweed has been classified as hazardous waste in the U.K. If you try to shred this photosynthesis phenomenom, pieces, check that, ONE piece can create 10 more plants in the area . . . all with massive root systems. So how does knotweed spread? From people unknowingly, and illegally, dumping garden waste, from contractors moving contaminated soil, and from mechanical flails and mowers. The tracks on a dozer can catch pieces and transplant the menace. The plant dies in the wintertime, but comes back every year. The problem is real and it is spreading across the U.S., and it could cost public works departments millions annually.

So what can be done? Knowledge is power. If you see Japanese knotweed in your city or community, report it. Create literature and deliver it to the population. Survey everything, and if you find it, cordon it off immediately and post signs screaming DO NOT CUT and DO NOT HANDLE. Accept Japanese knotweed as compost and prepare to be nuked. Communicate with nature centers and universities in your area. The trick is to get the weed in sleep mode. If you see it, professionally cut it in the spring and cover with a thick tarp three times the size of the contaminated area. It will continue to grow back, but tarp it up again and again and maybe, just maybe, you can get it to sleep. There are other forms of treatment. A good source of information is the Cornwall Council online. Of course, if you are seeing knotweed it is already too late. Cities and towns do not have the budget for this invasion, so you better not take what I say as just lip service.

About The Author: Wilson is editorial director of Roads & Bridges.

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