How can I safely dispose of soil that contains Japanese Knotwood rhizomes?


I live in Saco and am in the process of a multi-year (lifelong?) effort to control the spread of Japanese Knotweed on my property, using a combination of methods. My property abuts a community garden/park, which is infested, so I have no illusions of ever eradicating it but am trying to control its spread into my yard. Chemicals are not an option, as I’m against them and there’s a creek/storm drain between my property and the park.

I’m planning to dig a trench to prevent the knotweed from spreading into my lawn area. Whatever knotweed spreads underground past the trench will get mowed. My question: where and how do I safely dispose of the dug-up soil with rhizomes in it? I want to communicate to the landfill folks that this can’t go on compost and shouldn’t be used for fill dirt but considered as trash. I can try removing the visible rhizomes and double bag them separately, but there will still be remnants left.

The strip I plan on digging up has been mowed regularly for 5 years, so the rhizomes are relatively weak, and I plan to dig from mid to late April before shoots come up. Any guidelines on how deep to dig, and where to dispose?


Tori Lee Jackson, Extension Professor of Agriculture and Natural Resources

Digging out the rhizomes is not recommended because Japanese Knotweed can create a new plant from very tiny pieces of plant left in the soil. Repeated mowing/cutting (up to once/week ), raking up those plant parts and placing them in black garbage bags, and then leaving those tied bags in the sun for a few weeks should be sufficient to kill the stems and leaves. Even then, it should not go into a compost or burn pile. Not all landfills accept invasive species, so calling your local transfer station ahead of time is recommended.