With its towering height and vibrant pink flowers, Himalayan balsam (Impatiens glandulifera) might at first glance appear like a welcome addition to the British countryside. However, for landowners, developers, and conservationists, it poses a serious ecological threat.
First introduced in the UK during the Victorian period (1839), Himalayan Balsam was originally intended as an ornamental garden plant that ordinary people could obtain as a way of emulating the expensive orchids grown in the greenhouses of more wealthy citizens. However, it soon escaped the confines of cultivation and spread rapidly along England’s river systems, and is now classified as an invasive species.
This guide will explore how to identify Himalayan Balsam, as well as the legal implications of its presence and the most effective methods for its removal.
Identifying Himalayan Balsam: Key Features
Because it grows so rapidly, identifying himalayan balsam early is critical to preventing it becoming dominant. The plant completes its entire life cycle from germination to flowing, seeding, and death, within a single growing season, where it can reach up to 3 metres in height. Distinguishing features includes:
- Himalayan Balsam Flower: look for distinctive helmet-shaped blooms, typically in shades of pink to light purple, which typically appear between June and October.
- Himalayan Balsam Leaves: the leaves are long, narrow, and serrated, often growing in groups of three around the stem.
- Stems: the stems are hollow, fleshy, and green to reddish-pink, often described as bamboo-like in appearance.
- The Explosive Seed Pods: this is perhaps its most famous feature. When ripe, the seed pods explode upon touch, scattering up to 800 seeds as far as 7 metres away.
Is Himalayan Balsam Dangerous?
When it comes to humans and pets, the plant is not toxic to touch, nor is it poisonous to eat (though excessive consumption by dogs and cats can lead to gastric upset and vomiting). However, it does pose a threat to the environment.
By forming dense monocultures, Himalayan Balsam shades out native flora, leading to a reduction of wider biodiversity in the area. Furthermore, because the plant dies back completely in winter, it risks leaving riverbanks bare and vulnerable to erosion, which in turn can increase flood risks and damage local infrastructure.
Himalayan Balsam vs. Japanese Knotweed
Because both of these species are tall, fast-growing, and often found in similar habitats, they are frequently confused for each other. However, while both plants are invasive species to the UK, they each pose different risks.
Key visual and biological differences:
- While the Himalayan Balsam flowers are large, showy, and helmet shaped of a pink or purple colouration, Japanese knotweed produces small, creamy white flower clusters.
- Himalayan Balsam leaves are long, narrow, and arranged in groups of three, whereas Japanese Knotweed leaves are more broad and shield-shaped with a flat base.
- The stems of Himalayan Balsam are soft, hollow, and fleshy that appear green to reddish-pink, and can easily be snapped by hand. By contrast, Japanese Knotweed stems are much tougher and woody, and are far more structurally robust.
Structural vs. Ecological Risk
The biggest difference between the two species stems from the damage they cause. Japanese knotweed is notorious for its ability to grow through hardstanding, tarmac, and foundations, which can subsequently complicate property transactions and mortgages.
Conversely, the threat Himalayan Balsam poses is primarily ecological. While it won’t directly affect hard infrastructure it will significantly lower the biodiversity of a given area, and can cause riverbank instability.
Himalayan Balsam UK Law: What You Need to Know
Understanding Himalayan Balsam UK law is crucial for land managers. Under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise cause Himalayan balsam to grow in the wild.
While it is not illegal to have it growing on your private land, individuals and companies have a legal responsibility to prevent it from spreading to neighbouring land or into waterways. Failure to manage stands of the plant can lead to legal disputes and can even create constraints to achieving Biodiversity Net Gain (BNG) targets for new developments.
Under the same 1981 Act, it is also illegal to sell, offer for sale, or transport the plant or its seeds. However, a special permit or licence may be obtained from the Animal and Plant Health Agency (APHA) to cultivate the plant for specific reasons, such as for scientific research or conservation activities.
How to Remove Himalayan Balsam: Treatment and Timing
The principal aim of Himalayan Balsam treatment is to prevent the plant from dispersing and setting its seeds. This can be done by either pulling, cutting, or spraying the plants before they flower.
What is the best time of year for removal?
The ideal window for removal is late spring to early summer (between May-June). This is because, at this stage in its lifecycle, the plants are large enough to be easily pulled, but the seed pods have not yet fully formed.
Methods of remove include:
- Manual Removal: because their roots are shallow, ‘balsam bashing’, which effectively amounts to pulling the plant manually by hand, is effective for small stands of the plant.
- Mechanical Cutting: cutting the stems at ground level, generally with a strimmer / brush cutter before they flower can stop the lifecycle, though this may need to be repeated if regrowth occurs. This is an effective method even on large stands of the plant.
- Professional Herbicide Treatment: for large-scale or sensitive sites, professional services offering glyphosate-based herbicide control are advised to ensure the infestation is eradicated without damaging the surrounding ecosystem. Care must be taken however as herbicide treatment may not be appropriate in proximity to water courses, and will require specialist, regulator approved products..
How Thomson Can Support Your Project
Managing invasive species like himalayan balsam requires a proactive approach. At Thomson Environmental Consultants, we provide end-to-end support. These include:
- Utilising advanced digital mapping technology to track spread of invasive plant species and provide clear data to inform invasive species management plans..
- Offering compliance advice to ensure your site meets all the legal requirements and BNG targets where invasive species are present.
- Structured remediation from the initial survey to the final clearance. Our experts handle the heavy lifting to keep your project on track.
Suspect you have Himalayan balsam on your site? Contact our team today for a professional survey.
