River Nene Himalayan Survey

19 Jan 2013

They may be beautiful, but these big pink flowers are invading our local riverbanks!

Himalayan Balsam (Impatiens glandulifera), also known as Policeman's Helmet and Indian Balsam, was introduced into Britain in 1839 as a garden plant; however, it escaped and quickly invaded riverbanks. It grows in dense stands, killing any native plants which try and grow beneath it. Then when it dies back in the autumn it leaves the river banks bare and more vulnerable to erosion. Each plant can produce about 800 seeds in explosive seed pods that throw the seeds up to 7m from the parent plant. The seeds are easily transported along rivers, helping the population to spread. It is listed on Schedule 9 of the Wildlife and Countryside Act 1981 with respect to England and Wales, which makes it an offence to plant it or introduce it to the wild.

The Northamptonshire Biodiversity Records Centre (NBRC) are working with the Environment Agency to find out where Himalayan Balsam is growing along the River Nene. Everyone is invited to take part in a Himalayan Balsam survey to search for the Pink Invader.

How do I identify Himalayan Balsam?

Look for the large purplish-pink slipper shaped flowers along with a reddish stem and dark green leaves with jagged edges. It is easiest to see between June and August when it is in flower. They are found along rivers and can grow up to 2m tall.

The stems are hollow, fleshy and easily broken, and it has leaves with serrated edges.

The plants start to set seed from mid-July onwards and the seeds can remain viable for about 3 years.

Himalayan Balsam prefers to grow in moist and semi-shaded places, particularly on soft banks by slow moving water along streams, rivers and canals. It can also be found growing on waste ground and in thin woodlands.

How do I let you know I've seen it?

You can submit your sightings using this online form >>> or if you have lots of records you can note them down in this spreadsheet (.xls 19Kb) >>> and email it to us at nbrc@wildlifetrustbcn.org . It would be really helpful if you're able to send us any photos of the Himalayan Balsam plants you find to accompany your records.


Himalayan Balsam

The information we need is:

  • Where did you see the Himalayan Balsam?
    a. Location (nearest town/village)
    b. Description of location (e.g. Upstream and downstream of the weir near Ryehill Spinney)
  • Grid reference (at least 6 figure required please eg. SP729625. See http://tinyurl.com/grabagrid to help you get a grid reference easily)
  • The date you saw it
  • How much Himalayan Balsam did you see? (e.g. dense stands, quite a few patches or a few plants)
  • Your name
  • Contact details (which won't be given to anyone else and are only used if we need help in verifying a record)


The NBRC can be contacted at:
NBRC, c/o The Wildlife Trust for Bedfordshire, Cambridgeshire & Northamptonshire, Lings House, Billing Lings, Northampton. NN3 8BE
Telephone: 01604 400448


This information and more images can be viewed by downloading the information sheet (pdf 327Kb)