Action on invasive species in Calderdale

Managing invasive species

Reducing flood risk and boosting biodiversity in Calderdale.

Invasive plants like Himalayan balsam and Japanese knotweed increase flood risks. Because they die back in winter, they leave riverbanks bare, allowing rainwater to rush into our rivers and wash away soil.

By removing these species, we allow native plants to thrive. A healthy, green landscape stays covered year-round, which:

Slows down rainwater flow.
Prevents soil erosion.
Protects our local environment.

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

Working Together to Protect Calderdale

The Calder INNS sub-group leads the fight against invasive species. By working together, our partners target and treat problem plants strategically across the valley.

Our Recent Progress:

Japanese Knotweed & Giant Hogweed: Treated by the The Yorkshire Wildlife Trust and the River Stewardship Company (on behalf of the Environment Agency).
Himalayan Balsam: Extensive removal by Forus Tree and Calder Future.
Local Action: Many landowners are using our NFM Grant Scheme to remove invasive plants and reduce flood risks on their own property.

A Note on Giant Hogweed: While it doesn't increase flood risk, we treat it because its sap is toxic and can cause skin irritation.

How You Can Help

You can play a vital role in protecting Calderdale from invasive species. Your reports help us track, target, and treat problem plants more effectively.

1. Identify the Species

Before reporting, learn what to look for. Use these identification sheets to spot common invasive plants.

2. Report Your Findings

The most effective way to help is by reporting sightings via INNS Mapper app and website.

Download the App: The INNS Mapper app is available for free on all mobile devices.
Log a Sighting: Use the app or the INNS Mapper app and website to pin the location.

Important Safety Note: Do not attempt to remove Japanese knotweed or Giant hogweed yourself. These plants require professional treatment, and Giant hogweed sap is hazardous to your skin.

3. Alternative Ways to Report

If you cannot use the app, you can email your report (including the location and a photo, if possible) to the Yorkshire Wildlife Trust at: [email protected].

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.

Posters

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.