Will mowing Japanese Knotweed weekly kill the plant?


I noted that you posted a very interesting bulletin from New Hampshire on how to control knotweed in one of your question and answer sessions. In it, it notes that mowing alone will not kill it. What are your thoughts about this? I know that it has to be cut or mowed at least once a week. I am asking as I am doing some work on a field – trying to cut it down every week. Does this make any sense? 


Frank S. Wertheim, Extension Educator – Agriculture/Horticulture

You are correct in that mowing Japanese Knotweed in relatively flat terrain such as a field can control and starve out the plant. It is important to mow it frequently (weekly) and as low as you can set the mower. The strategy is that by mowing it regularly and not allowing it to establish a canopy of leaves you are forcing it to use the stored energy in the root system to grow new shoots. Every time you mow it you are forcing it to use more of that stored energy. Also by not letting it establish leaves it can’t feed the underground root system. It takes time and diligence but by being consistent you will weaken the colony of knotweed and eventually it will starve itself out and die.