Why do we need to clear Himalayan Balsam?

Across our farms, our volunteers and conservation team work tirelessly to remove Himalayan balsam. This striking but invasive plant, with its pink bonnet-shaped flowers and hanging green seed pods, poses a serious threat to our native ecosystems. 

Recently, at Bere Marsh Farm, we joined forces with Dorset Wildlife Trust to tackle this problem head-on along the banks of the River Stour, where both organisations own land. This vital task is necessary to protect local habitats. 

What’s the Problem With Himalayan Balsam? 

As the name suggests, Himalayan balsam is from the Himalayas and was introduced to the UK in 1839. 

It may have started as an ornamental curiosity, but it has since spread rapidly and aggressively, especially along riverbanks. Its fast growth and dense coverage allow it to outcompete native plants, creating a monoculture that disrupts delicate habitats. 

It appears on the Wildlife and Countryside Act 1981, Schedule 9 list and the Non-native Species Secretariat (NNSS) list of Species of Special Concern, meaning there are restrictions on growing, cultivating, selling and transporting it. 

Hannah Bosence, our farm manager at Bere Marsh, said: “We enjoyed teaming up with the Dorset Wildlife Trust to tackle this invasive species.  

“It’s a tough job to remove because of where it grows along riverbanks. We pull it by hand before the seed pods form and don’t use any weed killers. 

 “It is a relative of the Busy Lizzie, but it reaches well over head height, and it is a problem. It grows rapidly and spreads quickly, smothering other vegetation.” 

Its shallow roots also make riverbanks more vulnerable to erosion and flooding. When the plants die back, they leave disturbed and vulnerable ground that is easily washed away.  

On our farms 

At Pierrepont Farm in Surrey, together with the Surrey Hills National Landscape team, we recently hosted a corporate volunteer work party. Dozens of enthusiastic helpers pitched in to remove the balsam.

Corporate volunteer work party with Surrey Hills National Landscape team

At Lark Rise Farm in Cambridgeshire, the team has been tackling Himalayan balsam for many years.  

It was first noticed in 2002, when a few plants were seen, but, unfortunately, the potential impact of these plants was not appreciated at the time.  

Within eight years the plants had become dominant on the banks of the Bourn Brook and a plan to tackle it was instigated.  

The CRT is collaborating with The Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire, Cam Valley Forum and the Cambridge Conservation Volunteers to tackle the problem along the entire length of the Bourn Brook, with a focus on the headwaters initially, which means that effort is less intensive on the stretches around Lark Rise Farm, which is in the lower reaches.  

The project is part of a wider Bourn Brook restoration plan, which has already achieved great success in eradicating American mink, with a return of water voles as a direct consequence of this.

Cambridge Conservation Volunteers member Elena pulling Himalayan Balsam in the Bourn brook, Foxes bridge farm.

Vince Lea, our conservation officer at Lark Rise, said: “The project is focussing on removal from the upper reaches first, as this will make it less likely to recolonise by seeds spreading downstream if we can cut off the source in headwaters. 

“So most effort is going into the upper reaches and there is not enough time and resources to put in a big effort in our section just yet, so it gets a chance to produce seeds each year.” 

The CRT has about 4km of Bourn Brook and it is a very difficult environment to work in, explains Vince.  

 “It takes about 10 people to cover 1km in a five hour volunteering day if there's a lot of balsam, so we would need four well-attended volunteering days to do the whole of the CRT length, and we only have one session per month. It is only possible to find the plants in late June and they need to be eliminatemid-Augustid August, and with other volunteer requirements as well, it's just not currently possible.  

“In the upper reaches, where the plants have been reduced to nearly zero, it is much quicker to cover distance. We have achieved this by going twice a year, early in the season and late in the season, using Cambridge Conservation Volunteer and Wildlife Trust volunteer teams every week. It now takes a short day to cover 2km of bank. Once we have eliminated the plants from this upper area, we can focus these volunteer resources into the lower reaches. It's a big problem requiring a lot of effort!” 

Why should we remove Himalayan balsam if bees like it?

Vince added that some people see Himalayan balsam as a good nectar source for bees, and disagree with the idea of eradicating it.  

"However, studies have shown that bees get too obsessed with Himalayan balsam when it is available, and native plants in the area do not get pollinated, so this is another ecosystem disruption. The best hope for bees is the restoration of native wildflower meadows and this is what the CRT is doing,” says Vince. 

Vince also revealed that recently, it appears giant hogweed has been eradicated from the brook.  

“We are very pleased and grateful that all landowners along the Bourn Brook have granted the project partners access to their land to undertake this work, as any gaps in coverage would allow the plants to maintain a stronghold and colonise the rest of the brook,” he added. 

How You Can Help 

Removing Himalayan balsam is labour-intensive but makes a real difference.  

Whether you're interested in volunteering or supporting our conservation work, you can be part of the solution. 

To find out more about volunteering with the CRT, see www.thecrt.co.uk/volunteering 

How to support us

If you want to help us protect local wildlife and habitats, you can join as a CRT Friend, attend our in-person and online events and volunteer on one of our farms. You can also sign-up to our monthly newsletter 'CRT News' for regular updates from our farms, straight to your inbox.