Author Kevin Lerwill
Gatwick Greenspace Project Community Wildlife Officer
One of the most important jobs for us to tackle each Summer is trying to control the spread of himalayan balsam (Glandulifera impatiens) throughout the project area (and beyond) and with the help of our plucky volunteers we should have the people power to get it done. Himalayan balsam was brought back by Victorian collectors but is now a major problem along many of our watercourses for the following reasons:
- Balsam seeds are dispersed far and wide by explosive seed pods which can spread seeds over a seven metre radius around the plant, usually propelling them into a nearby watercourse to be carried down stream.
- After the seeds germinate in the spring, this impressive plant can reach up to eight feet in a little over 16 weeks, averaging six inches growth per week!
- To compensate for its shallow root system, balsam grows in dense stands, spreading quickly to dominate river banks, displacing native plants.
- This ability to smothers out all other vegetation has a knock on effect; when balsam stands die down in winter, river banks are left lacking the root networks which stabilise the soil, resulting in increased erosion, collapsing banks and creating a much greater flood risk.
- Though its flowers do provide nectar for insects, they are distracted from pollinating our native flora when they find large stands of pink balsam flowers. Native plants also have more structural diversity, providing better habitats for wildlife.
Over the years, the spread of himalayan balsam through urban and industrial areas has been left largely unchecked and this has been further compounded by recent flooding, distributing the seeds further and into previously unaffected territory.
Its not all bad news though; himalayan balsam only lives for a year, dying off in the autumn. The seeds remain viable in the soil for two years, so if himalayan balsam plants are prevented from setting seed for two to three consecutive years, this species can eventually be totally cleared from a site (provided it does not encroach again from neighbouring sites).
In conjunction with Gatwick Airport, our local authorities and as part of the River Mole Catchment Project (led by Surrey Wildlife Trust), we are now trying to make a concerted effort to reduce the spread of this invasive species from our area and you can help.
The simplest and most reliable management technique is to pull up this shallow rooted plant before it flowers and we will be doing this regularly throughout the Summer and into Autumn, so if you want to join the fight, please contact us for more information