To help protect biodiversity and natural habitats in the Lake District our Ranger teams are delivering an ongoing programme of work to tackle non-native invasive species.
What are invasive species?
Invasive species are plants or animals that spread into habitats where they don’t naturally belong and outcompete native species. They can be native or non‑native, as long as they grow or reproduce so aggressively that they dominate an area.
Most often, the term refers to Invasive Non‑Native Species (INNS)—species introduced to new places through human activity. Examples include Grey squirrels and Himalayan Balsam, which disrupt natural ecosystems and reduce biodiversity.
Native species often struggle to compete with these invaders. For example, the native red squirrel is declining due to competition from the non‑native grey squirrel.
Himalayan Balsam in Langdale Valley
Managing invasive non‑native species is essential because they threaten local biodiversity. One key example in the Langdale Valley is Himalayan Balsam—a tall plant with pink/purple “police‑helmet” flowers that thrives on wet, disturbed ground such as riverbanks.
As an annual, it grows quickly and produces thousands of seeds that burst from its pods, allowing it to spread fast. It forms dense stands that block light, outcompete native plants, and reduce insect diversity.
In Langdale, a wet woodland SSSI supports Touch‑me‑not Balsam, the sole food plant of the rare Netted Carpet Moth. Himalayan Balsam threatens this habitat, so rangers and outdoor volunteers spend many hours each year removing it to protect these important species.
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Tackling Invasive
Assistant Ranger, Bethany Brown talks about what we are doing to stop the spread of Himalayan Balsam, a non-native invasive species, in Elterwater, the Lake District. She shares tips on how to identify the plant and how to remove it.
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Video
Why do we manage bracken?
Bracken is a native plant that has become invasive in many upland areas. It naturally grows in woodland, where shade keeps it in check. However, widespread woodland clearance has created open, disturbed ground where bracken spreads rapidly, forming large dense beds.
Because it’s light‑loving, fast‑growing and has an extensive root system, bracken easily outcompetes other plants on the fells. It’s also toxic to grazing animals, so livestock avoid it, allowing it to spread even further.
We manage bracken to protect biodiversity, give other plants a chance to grow, and help restore a more natural balance in the landscape.
You can help us to tackle invasive species in a variety of ways. Use the guidance in this article around the identification and removal of different species in your own outdoor spaces or if you are out and about in the countryside.
Report sightings
If you spot Skunk Cabbage, Himalayan Balsam or Japanese Knotweed you can report it using the INNS Mapping Tool.
If you are going on the water on paddleboard, boat, other watercraft follow this advice to help prevent the spread of invasives in our waterways.
Check your equipment, boat, and clothing after leaving the water for mud, aquatic animals or plant material. Remove anything you find and leave it at the site.
Clean everything thoroughly as soon as you can, paying attention to areas that are damp or hard to access. Use hot water if possible.
Dry everything for as long as you can before using elsewhere as some invasive plants and animals can survive for over two weeks in damp conditions.
Volunteer
Interested in doing a bit more?We run regular outdoor volunteer days to tackle invasive species and do other essential conservation work including tree planting, hedge laying, surveys, planting wild flowers, dry stone walling, replacing gates and fencing. No previous experience is needed. Find out more about volunteering in the Lake District.
How to identify non-native invasive species?
See images and descriptions to help you spot American skunk cabbage, Himalayan balsam and Japanese knotweed, which are the three main species we are focussing on in the the Langdale & Grasmere areas.
Identification - Found in wet woodlands and around garden water features. Plants emit a strong, skunky odour. Big yellow flowers that look like wild arum (lords-and-ladies, cuckoo pint) with leathery leaves reaching 1m long.
Management - Small plants can be dug up but the roots of larger ones can be huge. With large scale issue management is focussed on foliar application of herbicide in May.
Identification - A tall annual plant found along water courses and damp grasslands. Each plant can produce hundreds of seeds that are catapulted once ripe so spreads very easily. It’s a threat to native plants species as well as causing excessive river bank erosion which can aggravate flooding. Plant grows up to 2m tall with large serrated leaves. Pink or purple trumpet-shape flowers and thick hollow stem on the larger plants.
Be aware - There is a native species Touch-me-not balsam (Impatiens noli-tangere) which has yellow flowers and rounder leaves. It’s a very important species for the rare Netted Carpet moth caterpillar.
Management - Balsam can be pulled up by the roots and left on site to decompose once the stems have been snapped between the nodes. It’s best to do this before the seed pods ripen. We carry out this work every 3-4 weeks during the summer on National Trust land around Langdale and Grasmere areas. We also work with others to manage it in different areas.
Identification – It is a fast-growing plant that was introduced to England from Japan as an ornamental garden plant in the 1800’s. It has strong roots and can grow back from even the smallest fragments of rhizome. Plants grow up to 3m tall and can form dense stands. Leaves are heart shaped and light green, arranged alternatively on zig-zag stems. The main plant stems are flecked with purple and have nodes similar to bamboo.
Management – We will do this for National Trust tenants The most successful method of eradication is stem-injection with a herbicide in September.
Do not cut strim, mow or dig it up if you have it your garden. It can be spread very easily, Do not put it in your garden waste bin or take it to your local refuse centre and you’ll be breaking the law.
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Search for live volunteering opportunities, or register your interest with Aira Force and Ullswater.
