When I lived in Short Beach, the neighbour 'down the road' was constantly at war with Japanese Knot Weed. He cut it off at the ground level only to have it grow back twice as fast in a month. He hired a tractor in early Spring to dig it up by the roots only to have it come back in the Fall. He even poisoned it plus his well and still it grew...one day he asked me what I would do to get rid of it. I told him to buy some pigs as they would eat it plus any roots. It would take a year and he would have two good size pigs to butcher or pets, whatever the 'wife' decided. He laughed.
I did add he could start eating it himself but he didn't like greens. He still have Knot Weed growing 15 years later on him property and he still waves to me when I pass...
(photo- tender new shoots of Knot Weed)
If you know Japanese Knot Weed has had poison applied, I wouldn't harvest it. It takes years for it to come out of top soil and could make you sick. If you have a personal patch, try this recipe : )