Himalayan Balsam: The Waterside Alien

I’ve recently been on placement with the ecology team at Nottinghamshire county council. I’ve learnt so much and I am looking forward to sharing all. So here is so info on the invasive species that I spent a lot of team working with:…

The pink flowers of Himalayan Balsam along our waterways is now a common sight… but it shouldn’t be. Himalayan Balsam, Impatiens glandulifera, is a non-native, invasive species, meaning that it originated from outside of the UK. As its name suggests it is actually native to the western and central Himalaya. When bought to the country in the mid-1800s as part of botanical collections for its beautiful pink flowers, it quickly spread across the country, sometimes through seeds being distributed by water courses but more often by the passing of seeds by collectors.

In the wild, it is often found on the soft banks of slow-moving water like streams and rivers, but it also likes damp, semi-shaded woodlands as well. Its distinctive pink flowers make it easy to spot along the banks during the summer, especially when they can grow to over 2m tall. The leaf edges are tinged with pink, as are the nodules along its hollow stem and the shallow roots are also a deep pink. Each plant can produce about 2000-3000 seeds and are dispersed by the seed pods exploding and casting the seeds a good distance from the parent plant. As they are an annual flowering plant, they die back during the winter.

Since its establishment in the wild, it has rapidly spread throughout the entire UK and is now threatening our native water-side plant species by outcompeting them through shading and crowding out native species. The highly attractive nectar-producing flowers of Himalayan Balsam also add another blow to native flowering species by pollinators, such as bees, preferring the Balsam over our native flowers, meaning native species are not pollinated well and do not produce enough seeds for the following year.

As well as threatening native species, Himalayan Balsam is also causing major damage to our waterways. During the summer, where there are thick clumps that overhang the water, it can often block waterways and increase the likelihood of flooding during times of high rainfall. Also, with its shallow roots and annual life cycle where it dies back during the winter, it often leaves waterways vulnerable to erosion during the winter, which destroys the homes of animals that live on the water’s edge, such as Water Voles. It also costs a lot of money to prevent or replace the erosion of banks and save bankside structures.

It is possible to remove this threat though. As part of a project by Nottinghamshire Biodiversity Action Group (Notts BAG), many volunteers have helped clear areas of Balsam by pulling it from the river banks. Starting at the highest point in Nottinghamshire District of Ashfield, many upstream areas of the rivers that flow through Ashfield have been cleared of Balsam. This includes the River Maun, the River Meden, the River Erewash and many others that flow throughout Nottinghamshire and eventually join up with the River Trent.

2016-08-09 14.11.13 HDR
Good old waders…

The plants have to be pulled several times throughout the summer to stop those that grow back from seeding. It’s important to start pulling the Balsam as far up the rivers as possible because the seeds flow downstream and would re-colonise a cleared patch if not monitored correctly. As the seeds are viable for about 2-3 years, it means that the same site has to be revisited for a couple of years afterwards to ensure that they are gone for good.

This project runs with the dedication of volunteers who come to pull the Balsam before it seeds during the spring and early summer. To get involved with the Himalayan Balsam projects in the Nottinghamshire area, please contact Chris Jackson from Notts BAG atchris.jackson@nottscc.gov.uk . Alternatively you can report a sighting of Himalayan Balsam in Nottinghamshire tobiodiversity@nottscc.gov.uk .

 

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