How can I safely dispose of soil that contains Japanese Knotwood rhizomes?
Question:
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?
Answer:
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.