A researcher at Humber College has discovered a spading method for destroying Japanese Knotweed that apparently seems to work:
1. Slice down at a slight angle into the soil beside the stem of the plant, cutting off the stem a few inches below ground. Don’t try to get the roots, and disturb the soil as little as possible.
2. Tamp the soil back in place, covering over the area. This deprives the plant of sunlight, weakening its ability to grow. But doesn’t break the roots off, which might cause them to regrow.
3. Repeat again 2 weeks later, and every two weeks until the plant is exhausted and gives up.