Himalayan Balsam: an unwelcome invasive species
Written by Sammy Haddock, Invasive Non-native Species Coordinator
Himalayan balsam is a beautiful plant. This is no doubt why the Victorians took a shine to it and brought it to England to put in their gardens. Little did they know the damage this plant would then cause in the years following. Himalayan balsam (Impatiens glandulifera) is an annual, meaning that each plant will grow for one year, set seed and then die off. The problem is in the number of seeds it produces – a whopping 800!
These seeds are in pods which can fire the seeds approximately 7m away. Then add in natural aids such as wind and water and you find these plants popping up all over the place. The seeds can stay dormant in the ground for a couple of years, so to completely get rid of the plant, you have to keep going back to ensure you’ve not missed one.
The impact on biodiversity
You might be wondering if the plant is so beautiful, why get rid of it? This plant outcompetes our native plants which reduces the amount of biodiversity (plants, insects and animals) in any one area. You will see bees using the Himalayan balsam flowers. This helps the bees but yet again will reduce the diversity of other plants. Bees are needed to help pollinate our native plants, so if the bees are busy pollinating this invasive species, they will not be pollinating our plants, therefore reducing the chances for the plants to reproduce.
The other major issue with Himalayan balsam is its roots. They are very small in comparison to the plant’s size, with roots only several inches long. Himalayan balsam typically grows between 4-10ft. However, one of our volunteers found one that was more like 12ft! The short roots along with Himalayan balsam outcompeting other species means that there aren’t any roots knitting together banks, such as along rivers or railway lines. This can then result in the banks collapsing.
The pictures below, taken by a volunteer (Ken Taylor) show an area inundated with Himalayan balsam in 2018 and how it looks now, in 2023.
‘Balsam bashing’ events
The South Cumbria Rivers Trust organise ‘Balsam bashing’ days where volunteers can come along and help eradicate Himalayan balsam. If you’d like to get involved, check out upcoming dates and locations on our Events page here.
The following pictures show the same location before and after a balsam bashing event. We tackled this site using scythes and also by pulling by hand. The photos demonstrate how tall the plants are, how dense they are and how little of any other vegetation there is.
For farms, this means less area for grazing their animals and for nature to flourish. The watercourse alongside is probably how this population of Himalayan balsam came to be on this site.
All the Himalayan balsam we pulled up or scythed was left in heaps as it is an offence to remove Himalayan balsam off site in case it causes outbreaks anywhere else. We try to ensure that the root base has been removed and any seed pods developing are in the heart of the pile. This prevents the seeds from travelling elsewhere. If the seeds do manage to produce a plant the following year, the plants will all be in one location and we can deal with them before they set seed.
For further information on invasive non-native species, how these affect the River Kent catchment and the work we are doing, read our Biosecurity page here.
