By Dr Vince Lea, Head of Wildlife Monitoring 

During the summer months, CRT volunteers have been clearing Himalayan balsam from the Bourn Brook on Lark Rise Farm as part of our joint venture with the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire (WTBCN). This project, launched in 2011, aims to reduce the impact of all non-native species on the brook, which rises near to the WTBCN headquarters in Cambourne and ends just downstream of Lark Rise  

Eradication is working really effectively with mink through the Waterlife Recovery East project, but Himalayan balsam is taking a lot longer because each missed plant can produce hundreds of seeds. We are seeing a great reduction in the problem, but it is still around.  

I led twelve Himalayan balsam pulling sessions over the summer, between June and August, with Cambridge Conservation Volunteers (CCV), the CRT’s volunteer group called The Rustics, and some corporate groups. WTBCN and The Cam Valley Forum also ran sessions. 

In the upper reaches, we only found one or two plants per hundred metres but areas got missed last year had hundreds of plants per metre! This shows how dense the plants can become if left unchecked, resulting in a lack of native plants. The presence of Himalayan balsam can lead to erosion of the riverbanks, because when it dies down in winter it leaves bare ground exposed to fast flowing water. 


Amy Wolstenholme, a new member of Cambridge Conservation Volunteers, is an enthusiastic convert to balsam bashing!  

Published: December 2022.