Action on invasive species in Calderdale

Managing invasive species

Managing invasive species is crucial for reducing flood risk and creating a more biodiverse Calderdale.

Himalayan balsam and Japanese knotweed die back in autumn and winter, leaving the ground bare. This allows rainwater to flow more quickly over the surface, increasing the risk of flooding. Removing these invasive species lets our beautiful native plants regrow and thrive, ensuring the land is covered year-round. This helps slow down rainwater on its way to the river and prevents soil erosion.

A sign that reads 'Attention, invasive plant, Japanese Knotweed'

Working in partnership

Efforts to combat invasive species along Calderdale's watercourses are led by the Calder INNS sub-group. This group unites various partners to strategically identify and treat invasive species.

The Yorkshire Wildlife Trust and the River Stewardship Company, on behalf of the Environment Agency, have treated Japanese knotweed. Forus Tree and Calder Future have extensively removed Himalayan balsam in the Calder Valley. Some landowners have also participated in the NFM Grant Scheme to remove Himalayan balsam and reduce flooding.

Although Giant hogweed does not contribute to flood risk, we are also working to control this invasive species in Calderdale because its sap can harm human health if it contacts the skin. The River Stewardship Company, on behalf of the Environment Agency, handles the treatment of Giant hogweed.

How you can help

There are many ways you can help us tackle invasive species in Calderdale. To learn more about why action is needed, please visit our Invasive Species page.

Report Sightings

The most impactful way you can help is by reporting sightings of invasive species on the INNS Mapper app and website. This is especially important for Japanese knotweed and Giant hogweed, as they require professional treatment and should not be removed by individuals. Here's how you can help:

Learn What to Look For: Use these identification sheets to familiarise yourself with invasive species.
Download the INNS Mapper App: The app is free to download and use.
Report Sightings: Use the INNS Mapper app and website to report any sightings.

If you are unable to use INNS Mapper, you can also email the Yorkshire Wildlife Trust at [email protected] to send your report.

Get involved in the action

Volunteer

Join fantastic volunteer groups like Slow the Flow and Forus Tree, which are tackling invasive species across Calderdale. Participate in a volunteering day to help clear invasives and create natural flood management measures. Check our News Page for upcoming volunteer opportunities.

Bash the Balsam!

Summer is the peak season for ‘balsam bashing’. Himalayan balsam has a very shallow root system, making it easy to pull out and snap. Doing this before the plant goes to seed can effectively stop its spread.

The Yorkshire Invasive Species Forum and Yorkshire Wildlife Trust have produced a guide to help you pull Himalayan balsam safely. Please avoid pulling Himalayan balsam once it has seeded, as bursting seed pods can spread seeds over several meters.

Treat Knotweed on Your Land

Do not attempt to remove Japanese knotweed yourself, as this can increase its spread. Professional treatment is required and can take several years to be fully successful. If you have Japanese knotweed on your land and need advice, contact the Yorkshire Wildlife Trust at [email protected].

Raise Awareness

Help us spread the word about invasive species in Calderdale. Download these resources to share through your networks.

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Social media graphics

Projects in Calderdale

An exciting initiative is underway in Calderdale to tackle invasive species.

Led by Calderdale Council, an experimental trial with CABI (Centre for Agriculture and Bioscience International) is taking place near Todmorden. The trial uses a natural control method to reduce the impact of Himalayan balsam.

In 2006, CABI began studying natural control methods in balsam’s native range, the Himalayas. They observed a rust fungus and selected it for an experimental trial. In 2010, a specific species of rust fungus was exported to a quarantine facility for in-depth safety testing.

Since 2015, this rust fungus has been introduced to 47 sites across England and Wales. The site in Todmorden has shown remarkable success, with the second most promising results among the test sites. Further studies and potential release of the rust will continue at this site. It is hoped that the rust is now established and will spread through airborne transmission.

This method aims to reduce the spread of Himalayan balsam without the need for extensive manual removal.