Control of invasive plants

The River Beane and the Stevenage Brook have serious infestations of Himalayan Balsam and Giant Hogweed. Japanese Knotweed can cause serious problems, but fortunately none has been found along the Beane yet.

Himalayan Balsam

Himalayan balsam out competes the native the plants. It is an annual plant, so when it dies at the end of the year the river banks are left bare which exposes them to erosion during high water flows in the winter.
The RBRA working in partnership with Herts and Middx Wildlife Trust and riparian owners is working to control and contain the spread of the Himalayan Balsam. This is best done by pulling the plants up (including the roots) and then folding and twisting the stems to break them up. They should then be place away from the water’s edge, to prevent them being washed downstream. They will rot very quickly. The best time to pull the balsam is during the months of June and July before the seeds are formed.

Giant Hogweed

Giant hogweed has a similar effect on the river banks and it is a serious danger to humans. Contact with the plant can cause severe blistering of the skin. It has a three or four year life cycle, producing huge flower heads on a 2 – 3meter stem during the final summer of growth. The most effective control method is to spray with a systemic herbicide.
The RBRA is working in partnership with the Environment Agency, Lafarge, Woodhall Estate and other riparian owners to control and hopefully eradicate Giant Hogweed.

If anyone has Himalayan Balsam, Giant Hogweed or Japanese Knotweed on their land and you don’t think the RBRA knows about it we would like to hear from you, we may be able to help.