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Welcome to Verity Webster, Ecology & Protected Species Consultancy - Click to call 07917 852401
Welcome to Verity Webster, Ecology & Protected Species Consultancy - Click to call 07917 852401
Welcome to Verity Webster, Ecology & Protected Species Consultancy - Click to call 07917 852401
Welcome to Verity Webster, Ecology & Protected Species Consultancy - Click to call 07917 852401

Article - Himalayan Balsam

An Invasion of Non-Native Species

Recently, as part of my freelance ecology consultancy work I was lucky enough to have the opportunity visit Wigan Flashes Local Nature Reserve (LNR), Lancashire as part of an Ecological Appraisal (or Phase 1 Survey). I later made a return visit at the weekend so I could spend more time wandering the pathways between the various habitats, which include open water, willow carr, marshland and grassland. It is a diverse, quite magical place, the winding pathways luring you further into the maze of natural wonders. I certainly recommend it for a good day out.

I must say, however, that my Ecology / Phase 1 Survey trip for work, which allowed me to investigate more closely the depths of the willow carr (quite vulnerable to disturbance so not visited by the general public), was more fascinating than later wanderings. Part of the allure for me was the necessity to push and duck my way through the dense tree branches like I was entering a secret world, before it opened now and again into small sunlit clearings. Underfoot it was very wet and I had to take care not to sink into the bog dominated by sphagnum mosses (Sphagnum palustre and S. squarrosum included).

Scattered glittering pools supported ferns such as narrow buckler-fern (Dryopteris carthusiana). I would be more than happy to do a more detailed botanical survey there. Birds twittering overhead include the willow warbler, chiffchaff, coal tit and blue tit - truly enchanting.

Whilst I was adventuring, however, I noticed that one plant was particularly abundant. Presently still small, each plant would soon be taller than me. It was none other than the famous Himalayan balsam (Impatiens grandulifera), an alien to the small, magical world of willow carr, and a big threat to many native habitats.

Himalayan balsam (Impatiens grandulifera)

[image courtesy of The Lancashire Wildlife Trust]

What is Himalayan Balsam?

Himalayan balsam is an invasive species and was introduced in the mid-19th century as a garden ornamental. It is a beautiful plant, I shan’t deny that, but it's non-native and - as is a common story - has found its niche in a new world and, without any means of natural control, it has begun a rampage. Himalayan balsam is now regularly seen along watercourses and wet habitats across the UK. I often note its presence whilst undertaking my Ecology Appraisals (or Phase 1 Surveys) around Manchester and the Northwest.

A Pretty Alien

Himalayan balsam is, for all intense purposes, a giant 'Busy Lizzie' of genus impatiens. It is one of the tallest terrestrial annual plants in England, growing up to two or three metres in height. The leaves are oval, pointed and toothed with a purple tinge to the veins. They are opposite or in whorls of three around the near-translucent stems. In flower the plants are stunning, producing an inflorescence supporting several pale pink-purple flowers with a lower split lip and a hooded upper petal. Later in the season it produces black, elongated seed pods which explode open if touched, giving the plant its other common names of Jumping Jack and Touch-Me-Not.

Why is it a problem?

Himalayan balsam favours damp woodland, flushes and mires - irrespective whether the ground is shaded or open. There is a lot of this type of habitat in the northwest of England in Lancashire, Cheshire and Cumbria. Where present it forms dense, continuous cover, shading out all plants beneath it and therefore resulting in damage to our delicate, native plant communities and ultimately reducing biodiversity. When the plant dies-back in the autumn, the riverbanks are devoid of vegetation and are more susceptible to erosion over winter.

A study by Tanner, R.A. et al (2013) has shown a reduction in the abundance and species richness of above-ground invertebrates where Himalayan balsam is present, so it has a knock-on effect to the whole ecosystem. Each plant can produce up to 800 seeds and part of the reason for such quick spread is the fact that its seeds float, so any linear watercourse provides prime dispersal opportunities. The seeds can even germinate before they reach new ground.

It’s not a complete disaster though, as the plant provides some real benefits for many of our native bumble bees who love the nectar rich flowers. This is because bumble bees are originally from the Himalayas (maybe that is why they are so fluffy) and so have evolved in concurrence with the Himalayan balsam plant.


Schedule 9 of the Wildlife and Countryside Act 1981 (as amended) lists all invasive species in the UK. Himalayan balsam is on Schedule 9, along with Japanese knotweed (Fallopia Japonica), Giant Hogweed (Heracleum mantegazzianum) and many other plant species -, more than 39 in total -, including invasive water plants such as New Zealand pigmyweed (Crassula helmsii), Parrot’s feather (Myriophyllum aquaticum) and all in genus Elodea (waterweeds).

It is an offence to release or otherwise cause these species to grow in the wild. New EU legislation on invasive species (Regulation 1143/2014 on invasive alien species) came into force in January 2015. The EU regulation identifies three types of intervention; prevention, early detection and rapid eradication, and management.

Some of the ways the regulation will be implemented in the UK is through more rigorous application of the current legislation (e.g. Wildlife and Countryside Act 1981; Wildlife and Natural Environment (Scotland) Act 2011; EU legislation) prohibiting the release of non-native species to the wild, improving detection and monitoring of invasive species, improving detection at UK boarders, improving education of the public and improving management and control techniques. New legislation in the UK will allow the Environment Agency to enforce species control orders onto land owners in some circumstances.

For this reason, if you are managing or developing land, it is important to be aware that invasive species might be present. The presence of these species can be picked up when a Preliminary Ecological Appraisal or Phase 1 is undertaken, or when a BREEAM Ecological Assessment is undertaken. If you need a specific Ecology Survey just to pick up Invasive Species, this is can be done also. Mitigation and Management recommendations would be provided in an Ecological Appraisal or Phase 1 Survey.


Control is very difficult owing to the great spread of the plant. Some areas are sensitive (such as SSSIs and European Designated Sites) and others are inaccessible. Chemical control is often used, but is not advisable due to the damaging environmental impacts and the close proximity of Himalayan balsam to water courses. Consent to use specific herbicides near UK waterways must be sought from the Environment Agency.

Removal of the plant by hand can be undertaken, but is not a long-term solution. Long-term management on nature reserves often involves cutting of the plant and removal of arisings prior to its setting seed.

A New Hope – Rust Fungus

The rust fungus (Puccinia komarovii var. glanduliferae) lives on Himalayan balsam and completes its life cycle on the invasive plant. The fungus has five different spore types in its life cycle, all of which require Himalayan balsam, and that plant alone. The rust fungus infects the stem and leaves of the plant through the growing season, ultimately killing it.

The rust fungus has been heavily studied, has undergone many trials and in 2014, was deemed a suitable candidate for release as a method of biocontrol (Tanner R. A. et al 2015).

In 2014 the CABI (specialising in agricultural and environmental research) released the rust fungus at three sites in the south of England. They did this by planting eight infected plants at each site. Monitoring showed positive results, including evidence of natural spread of the rust fungus to adjacent Himalayan balsam plants. The release study is on-going and new sites have been identified for trial this year. This is a major breakthrough for control of Himalayan balsam and looks very promising for our native flora.

Get in Touch!

If you would like an Ecological Appraisal (or Phase 1 Survey), Botanical Survey, Invasive Species Survey or BREEAM Ecological Assessment, or would just like advice on Invasive Plant Species, just give us a call on 07917 852401 or send us an email.


Tanner, R.A; Pollard, K.M; Varia, S; Evans, H.C; Ellison, C.A. (Feburary 2015) First release of a fungal classical biocontrol agent against an invasive alien weed in Europe: biology of the rust, Puccinia komarovii var. glanduliferae. Plant Pathology.

Tanner, R.A; Varia, R; Eschen, R; Wood, S; Murphy, S.T; Gange, A.C. (2013) Impacts of Invasive non-native annual weed, Impatiens gladulifera, on above- and-below-ground invertebrate communities in the United Kingdom.

PLoS ONE 8(6): e67271



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