Invasive Non-Native Species (INNS)

Gloucester City Council is embarking on a project to control an invasive non-native plant along the watercourses in the city.

Himalayan Balsam

Himalayan Balsam was introduced to the UK in the 1800’s and now poses a threat to our native flowers and vegetation.  Himalayan Balsam can quickly take over large areas by forming dense vegetation that will shade out native plants and following its die back in winter leaves bare earth that will be prone to erosion.

The plant typically grows in damp environments such as riverbanks and spreads through seed dispersal with each single plant having the potential to produce 700 seeds.  These seeds can be propelled over 7m.

Himalayan Balsam is an annual plant which means it grows, flowers, seeds and dies back all in one year.  It has shallow roots that provide little protection to riverbanks from erosion while its nectar is highly desirable to pollinators at the expense of other local native plants.

Himalayan Balsam flowering

Himalayan Balsam pre-flowering (best time to control)

Gloucester City Council is looking to engage with volunteers and the public to raise awareness of the plant and help control it on our watercourses.  One of the most effective methods to control the plant is to pull it out of the ground prior to the seedpods forming.

Himalayan Balsam flowering with seedpods

Gloucester City Council, together with Gloucestershire Wildlife Trust,  will be arranging “Balsam Bashing” days during June and July  over the next couple of years to help show volunteers and members of the public some basic identification and control methods.  If you would like to know more, please contact us at

For information, please look at our Himalayan Balsam leaflet (PDF, 2.1 MB)  or those produced by GB non-native species secretariat (The NNSS Himalayan Balsam (PDF, 5 MB))

Upcoming Events

Any volunteer or 'Friends of' groups interested in joining in should contact Gloucester City Council by email

The next Balsam Bashing event will be held at the following locations subject to confirmation and weather. Events may be cancelled in extreme weather conditions such as heat or rain.

  • All times to be confirmed
  • Wotton Brook - Barnwood Park on Thursday 6 June 2024
  • Wotton Brook - Armscroft Park on Wednesday 12 June 2024 (10am to 1pm)
  • Sud Brook - Saintbridge Pond Friday 7 June 2024
  • Sud Brook - Linnet Close June 2024 (TBC)
  • Sud Brook - Awebridge greenspace June 2024 (TBC)

Volunteer Checklist

Please be aware that this exercise will involve entering the watercourses and some light manual lifting.  We have a limited number of waders, gloves and hi-vis waistcoats available for use on the day. If you wish to attend please consider bringing with you:

  • Water (for drinking)
  • Sunscreen and hats (for shade)
  • Personal medication (for hay fever and such)

Previous Events

June 2023 Wotton Brook volunteers at Barnwood Park