Words by Louise Barnetson, Water Champion for Parishes & Communities (Western Sussex Rivers Trust/Downs to the Sea)
If you go down to the river during the summer months, you may spot a tall plant with pretty pink flowers and a stalk that looks a little bit like a cross between celery and bamboo.
You may even see some determined groups of volunteers getting together to pull it up by the roots. Sometimes ‘those in the know’ even take it upon themselves to pull out the odd plant whilst walking the dog.
But why would anyone want to destroy such a pretty plant?! The reason is because this is Himalayan Balsam (Impatiens glandulifera, also known as Indian balsam, policeman’s helmet, touch-me-not, ornamental jewelweed), and it’s a menace to our rivers.
Himalayan Balsam is an Invasive Non-Native Species (INNS), that grows along riverbanks and in wet areas.
It is an annual plant that grows very quickly, from a tiny seedling in early spring to up to 7 feet in height by July or August. It out competes most native plants for light, water and nutrients. It spreads itself rapidly via hundreds of seeds that are catapulted out of pods in late-summer and autumn. It then dies back in the winter months, leaving bare soil and lots of seeds ready to germinate come next springtime. It has very shallow roots and the bare soil it leaves behind is prone to erosion, causing sediment to get washed into the river and increasing the likelihood of pollutants entering the water.
As the name suggests, Himalayan Balsam is native to the Himalayan foothills. It was introduced to the UK in the 1840s by Victorian botanists - and became a popular garden plant; however, in the 1950s it escaped into the wider natural environment and can now be found across 90% of the country. It is an offence to plant it or introduce it to the wild.
Many rivers and streams within WSRT’s catchment area are impacted by Himalayan Balsam infestations, including the River Rother, River Arun, River Ems, and Bosham Stream.
Earlier in 2026, through the Downs to the Sea project, we worked with the South Downs National Park Authority to deliver Himalayan Balsam training for local conservation groups and parish councils around the River Rother catchment area, where Himalayan Balsam is a particularly big problem.
Two events attracted around 50 representatives of local community groups and parish councils who were shown how to recognise Himalayan Balsam, why it needs to be managed, how to lead volunteer tasks safely, and were provided with information about biosecurity and safety (including practical demonstrations and practice of how to use throw lines).
We also distributed information packs and starter kits containing equipment and PPE to allow local groups start tackling Himalayan Balsam. Since then several groups have held ‘balsam bashing’ volunteer work parties across the summer with the aim of getting on top of the problem.
Whilst this work was focussed on the River Rother, we have also been able to provide support and information to other community groups outside that area who are interested in protecting their local waterway from balsam infestation, including the Friends of Bosham Stream, through the work of the Downs to the Sea Water Champion role.
If you are part of a community group or parish council that missed out on this year’s training events, then do get in touch as similar opportunities will be available next year.
Please contact the Downs to the Sea project at downstothesea@southdowns.gov.uk for further information. You can also help by reporting any sightings on an easy-to-use App called INNS Mapper.
In the meantime, keep your eyes peeled for the pink pest!
