Are there any cover crops that will keep Japanese Knotweed growth down?
Question:
I am trying to find a good cover crop plant for my yard that will keep Japanese Knotweed growth down. Clover is popular right now so that was on my mind. If there are any native plants that might outcompete Japanese Knotweed, I would love to know!
Answer:
Jonathan Foster, Special Project Assistant
Japanese Knotweed (Fallopia japonica) is a headache for home- and landowners all over Maine, so while I’m sorry to hear you’re having trouble, you certainly aren’t alone!
Unfortunately, one of the reasons it’s become such a nuisance is that it grows quickly under a wide variety of conditions, and generally outcompetes everything else. This Maine DACF publication recommends repeated cutting/mowing of the shoots, possibly with the addition of glyphosate (depending on your comfort level with chemical interventions), as the most effective method of control. It may take a while, but there are very few plants that can survive indefinitely without access to the photosynthetic machinery of their foliage. Be careful about tilling or physical removal of the plant, as broken rhizomes (the spreading underground stems) will simply resprout as new plants.
However, don’t let me dissuade you from introducing clover to the area, as it’s a nice alternative to turfgrass for those seeking to decrease their lawn care efforts and every bit of competition can help. But it probably won’t solve your knotweed problems.