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Grantham RiverCare volunteers and partners are on a mission – to stop ‘space invader’ Himalayan Balsam




‘Space invaders’ are the topic of this month’s Tales from the Riverbank column by Grantham RiverCare co-leaders David Martin and Ian Simmons. They write:

Around this time of year our #riverheroes go a-hunting invaders from another planet. Or rather, a-hunting another plant!

This goes by the name of Himalayan Balsam and, by it’s very name, you can see that it isn’t from around these parts.

Grantham RiverCare co-leaders David Martin (left) and Ian Simmons
Grantham RiverCare co-leaders David Martin (left) and Ian Simmons

These invasive species are the problem we face along our riverbank and across the country.

It is, by any measure, a handsome plant with bright, orchid-like purple flowers that tower over local vegetation. It is also very robust and successful. This is, in part, due to it’s explosive propagation method with seeds, literally, launched metres across an area.

There is some evidence that Balsam may also excrete poisons that negatively affect neighbouring plants, increasing it’s competitive advantage.

It was introduced by travelling Victorians in the early 1800s with other invasive species including Giant Hogweed and Japanese Knotweed, with the former containing toxic sap and the latter causing particular issues as it’s irradication is even more difficult.

Balsam negatively affects our local rivers because its size dominates other plants. It then dies back in winter exposing riverbanks to erosion, further exacerbating the issue. This interface between the river and land is known as the riparian zone and the plants that grow here are known as riparian vegetation, especially evolved for this interface.

Local volunteers, led by Grantham RiverCare and guided by Lincolnshire Wildlife Trust and East Mercia Rivers Trust, have been seeking out and destroying this plant over the last few years – we call it “Balsam bashing”!

A local hotspot is towards Harrowby Mill and there is a thriving population of Balsam within the grounds of Belton House. We are happy to report that this year’s survey has shown that our work has gradually reduced the population and hence threat to the greater local ecosystem.

As ever with Nature, the answers and solutions to a problem are not seen in isolation. For example, one practice that will help slow the spread of Himalayan Balsam is to reduce fertiliser run-off from agricultural land.

Additional nutrients in water courses enhance the growth of the invaders at the expense of local vegetation that are adapted to lower levels of available nutrients.

In the meantime, while some farmers recognise that the lower input style of farming, often called regenerative agriculture, will help the environment generally (and save money), local awareness of the problem with ‘space invaders’, particularly from June to August, is still hugely important.



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