Himalayan Balsam survey report published

Himalayan Balsam at Audley End overspill loop

Download full report here

In 2019 Cam Valley Forum volunteers (led by Mike F)  carried out a catchment wide survey of the incidence of the invasive weed Himalayan Balsam.  The primary aim of this survey was to identify the key upstream hotspots on which eradication effort should be focussed.

These upstream hotspots are

  • Sparrow Hill (TL521364) north of Newport
  • Madgate Slade and in adjacent overspill ditches at Saffron Walden (TL531383).
  • SSSI site ‘Alder Carr’ at Hildersham, (with a few plants above this)
  • Coton Nature Reserve at TL414582.
  • Bourn Book (active eradication programme underway by WLBCN, CCV CRT and CVF)

Cam Valley Forum will be focussing on the areas adjacent to Cambridge, particularly Bourn Brook and downstream into Cambridge City but we hope our partners; the  Environment Agency, local Wildlife Trusts and conservation groups, will find this report useful in tackling the other upstream hotspots.

Himalayan Balsam is a problem because it is an extremely invasive non-native annual plant. It grows well in moist and semi-shaded damp places, predominantly on the soft banksides of slow-moving watercourses. Where it becomes dominant it can cause environmental problems:

  •  reduces biodiversity
  • can choke waterways leading to flooding
  • competes with native flowers for pollinating insects–especially bees
  • when killed by frosts, it leaves ground bare and vulnerable to erosion leading to bank loss and unwanted sediment in the water

Resources to help with eradication available here