Considering the recent escalation of knotweed along the Housatonic River corridor, River Walk would like to share what we have learned, while working for twenty years to manage this exotic-invasive plant.
When the River Walk began its downstream section, 650 linear feet of riverbank were entirely infested with mature knotweed (8’ high), between the adjacent parking lot and the river’s edge. As we are situated directly on the river, River Walk’s policy is to use no chemical treatments of any kind.
After trying several mechanical techniques (soil replacement, removing roots, etc.), we settled on a multi-pronged, labor-intensive method with good success. We hand-cut knotweed 3-4 times per season, preventing it from flowering and producing seed, while introducing shade through native plantings as quickly as possible. We let the cut knotweed lay on the ground. Now that it is under control, but not eradicated, we continue to cut out occasional plants that appear. If an event such as a tree fall reintroduces sun, we are more aggressive in our native planting and weeding.
Experience has taught us that reclamation activities are only successful when attention is paid over time. Two or three years of intensive action will bring the situation under control, but some level of repeated management will likely be needed to control the ubiquitous plant in the long run.