Now how do I put this without upsetting anyone????? Oh yeh, it's a futile gesture. It might make the ones doing feel good and they have done a grand job but futile all the same.
The seedbank in the ground on most rivers in the UK is stuffed full of seed. Seed that can and does stay dormant for years. One exploding pod has about 20 seeds in it on average and a plant can have 200+ pods.
Rivers by their action move that seed around during the autumn floods and the sediments containing it in a conveyor action. So you can see the only way to eradicate is to is to remove it from the seedbank of the whole river and that is nigh on impossible.
Honey btw from bees that have collected from the plants is well prised by beekeepers.
Cows also like eating the plant, it's sweet and contains plenty of freshwater in the stalks.