Himalayan Balsam is a problem on the Greenway. As an invasive species it tends to take over from native species and destroys bio-diversity. See the RHS site for detailed information.
There is as yet no safe chemical or biological control agent so control depends on volunteers lifting the palnts before they seed. It is so prevalent it is impossible for us to eliminate it so we focus on keeping it off the verges. A few years ago the section from Naburn Bridge to Naburn Station was over-run but is now Himalayn Balsam free. Look down the embankment however and you will see it flourishing, so each year the struggle renews as it tries to re-colonise the path.