For the past 30 years, Japanese knotweed has steadily tightened its choke hold on our land.

We used to feed its young leaves to our rabbits; they loved it. In the spring, we put leaves in our salads. Delish! Agronomist Isabelle Martineau in Abercorn makes a lemonade from young shoots; she boils it, adds lemon juice and sugar, and calls it ‘‘Renouée.’’ Tastes like rhubarb, she told CBC.

But all these uses, and even a law against its propagation, have not stopped its steady spread.

I know what doesn’t work, as I explained in my last column. Chemicals don’t work. Mowing, rototilling, and composting all spread it. Don’t be tempted to dig out the roots; they can extend more than three meters deep and seven meters away from the plant’s stem.

Now we have embarked on the long, hard war to reclaim our land for indigenous species.

Here’s what to do: First, exhaust the energy the Japanese knotweed plant stores in its rhizomes by cutting the stems close to the ground … repeatedly, every two or three weeks during the growing season.

Next, you need to cover the whole area with a heavy-duty, opaque black geotextile membrane, also known as a tarp. Make sure the tarp extends at least two meters beyond the edges of the thicket, and weigh the edges down with rocks or logs. Leave the whole area covered for at least five years.

You’re not done yet. Clean your tools. Make sure all the dirt and debris is cleaned off your shovels, pruners, boots, and tires so you do not inadvertently transport a growth bud to another location.

What to do with the cuttings? Put all the stems, pulled-out roots, and surrounding soil into thick, sealed, black garbage bags. Dehydrate the branches by letting them sit, open, under the sun, in as much heat as possible, before closing the bags securely.
Never put Japanese knotweed in your green bin, brown bin, or home compost. It must go into an engineered technical landfill, such as that created by Valoris. Or, if you dig up soil containing roots, you can try burying it on-site at a depth of at least two meters. Yikes.

For details, see quebec.ca/agriculture-environnement-et-ressources-naturelles/flore/fiches-especes-floristiques/renouee-japon. Also, identify Japanese knotweed and other invasive species, and report them, at the Sentinel catalogue, pub.enviroweb.gouv.qc.ca/scc/Catalogue. Like I said, it’s a long, hard war.