Giant Russian Hogweed plants were noted along the banks of the Dargle River in Bray, Co. Wicklow in Ireland at least twenty years ago. Beautiful to look at - but dangerious to touch - as many a small local child was to discover to his/her cost. The local kids managed to make pea-shooters with the hollow stems - resulting in facial burns. The theory is that Soldiers returning from the First World War brought the seeds into Ireland on their muddy boots. The plant is dispersed by water - hence its propensity to flourish along riverbanks - particularly in Ireland. I have seen the dreaded weed twice in Yorkshire. In one case, it was a lone plant growing besid e a road, in a rural area. The other sighting - was a hogweed nightmare. It had grown so tall and bushy -that it took over the river, well Beck as streams are called in this part of the U.K. I am unaware of any way in which to "dispose" of the plant long-term.