The one with this summer’s second Balsam Blitz…

On the upper Wandle where our previous cleanups have successfully removed most of the rubbish, the main threat to the river’s health is now Himalayan balsam.

This invasive non-native species is a tall fast-growing annual plant with sweet-smelling pink or white flowers that spreads easily by producing explosive, floating seed pods. It damages biodiversity and rivers by over-shading native plants: its sweet smell also attracts bees more than many native species, so their flowers receive less pollination.

After wrecking native plant communities, Himalayan balsam then dies back in winter, destabilising riverbanks because the soil is no longer held together by deeper native plant roots. Soil from the banks is eroded by winter floods and dumped into the river gravels as silt, suffocating invertebrates and fish eggs.

Fortunately, there’s a solution to this problem, because Himalayan balsam’s shallow roots make it easy to pull up…

… and its seeds only survive two or three years in the soil. This means that we can start pulling it at the top of the Wandle catchment, gradually forcing it further and further downstream until we reach the Thames.

Having started this botanical cleanup on the Croydon arm of the Wandle during the Wandle Valley Festival, we came back to this area for our July cleanup to conduct the next stage of our blitz, and clear any more balsam that had appeared since June, as part of Sutton’s Take Part, Take Pride programme.

Pleasingly, very few new balsam plants seemed to have sprouted in the last month, but one or two had spotted their chance and shot up to six feet or more!  Needless to say, John wasn’t impressed, and soon put paid to such ambitions…

After this second sweep, we plunged into the untouched jungle of stinging nettles and balsam downstream…

… where Gideon showed Erica his novel floating-wheelbarrow technique…

…and Bella did the rounds with bottles of water to keep us hydrated:

Sally’s raspberry cake proved a great hit at coffee time…

… and we sat chatting in the sun for a good half hour…

… before tearing back into the tropical groves of balsam all the way down to the little weirs below Richmond Green, and re-seeding the whole area with a native grass and wildflower meadow mix including buttercups, cowslips, selfheal, wild marjoram and oxeye daisies:

This was a WATER river rehabilitation and restoration event selected within the scope of the INTERREG IVA France (Channel) – England cross-border European cooperation programme, co-financed by the ERDF.

And as we surveyed the piles of balsam and rubbish we’d collected, we all agreed: it was worth all the heat, stings and scratches just to see this stretch of the Wandle on its way back to proper health and biodiversity!

Thanks to all our volunteers: Barry, Carol, David, Debbie, Diana, Erica, Gideon, Helen, Jan, Jo, John, Marcia, Neil, Roger, Rosie, Sally, Sue, Tim and Theo

… and thanks as ever to Sandra and our friends at Sutton Council for collecting and composting the balsam for us, as well as dealing with a small pile of rubbish: 6 bags, 1 carpet, 1 kitchen cabinet and 1 shopping trolley.