Himalayan balsam

Impatiens glandulifera

Overview

Photo credit: ©GBNNSS

Impatiens glandulifera

Habitat:

It inhabits riverbanks and areas of damp ground.

Widely Spread Species:

Under Article 19 of Invasive Alien Species Regulation (1143/2014) Himalayan balsam has been identified as a Widely Spread Species in Northern Ireland and as such, management measures will be put in place to minimise its impacts.

Description:

It can form dense monospecific stands where individual plants can reach 2 – 3 m in height (one of the tallest annual plants in Ireland)
The stem of the plant is smooth, hairless and hollow
They grow upright, easily broken and are usually purple in colour with many large oval-shaped pointed leaves bearing teeth around the edges
The flowers of this plant can vary in colour but are usually shades of white, pink or purple
Flowering usually takes place from June to October
Seed capsules arise when the flowers are mature and when ripe the slightest touch causes these fruits to split open explosively dispersing seeds up to 20 feet from the parent plant
Seeds are capable of further dispersal by water and animal and human aid.

Download NIEA ID guide

Origin and Distribution:

The plant is native to the western Himalayas but is now invasive in many parts of continental Europe
In Britain, Himalayan balsam is regarded as one of the top-ten most wanted species that have caused significant environmental impact

Impacts:

This species grows in thick monospecific stands, shading out native plants such as grasses
From October onwards, the plants die back leaving the soil more exposed to erosion because of the loss of native plants earlier in the year
It has also been shown to produce more nectar in its flowers than native species making the plant more attractive to bumblebees resulting in less pollination of our native species - this can also, misguidedly, encourage some beekeepers to cultivate it illegally

How did it get here?

Originally brought into Northern Ireland as an ornamental garden plant.

Is it found in Northern Ireland?

The species is now widespread in Northern Ireland.
More distribution information can be found on the NBN Atlas NI.

You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.

Management Techniques: Manual pulling/cutting; commonly known as ‘balsam bashing’ events are now common place

It is vital to remember that pulling should be performed prior to the formation of the seed pods which explode at the slightest disturbance when ripe
Himalayan balsam has a very shallow root making uprooting by hand easy
The pulling technique must be undertaken so that whole plant is uprooted and normally best done if pulled from low down the plant - If snapping occurs at a node the pulling must be completed to include the roots
Uprooted plants can be left to air dry and decompose on a non-permeable membrane. This method is highly suited to dealing with initial outbreaks of the species and in areas where balsam plants are mixed in with sensitive native species
Mechanical control, by repeated cutting or mowing, is effective for large stands, but plants can regrow if the lower parts are left intact. The plant must be cut below the lowest node to stop regeneration
Strimming and mowing of Himalayan balsam may also be effective but only prior to the seed pods developing.
Any attempt to cut this plant once the seeds have developed will cause the seed pods to burst, spreading the plant.
The seeds of this plant are not very robust and only survive for up to 18 months, therefore a two year control programme can be successful in eradicating this plant provided there is no further infestation from upstream or adjacent sites
Grazing by cattle and sheep is effective from April throughout the growing season in some situations
It should be continued until no new growth occurs
Grazing on riverbank habitats can however have negative impacts such as poaching of river banks and the removal of other native vegetation which may act as a buffer zone

Treatment with Herbicide:

Where in situ physical removal is not feasible, potentially due to stand density/size or location/inaccessibility, the species can be successfully treated with herbicide.
Several herbicides have been shown to be effective at killing Himalayan Balsam and often just one application is sufficient. Nevertheless re-application in the same season should be planned for, as new growth from seed is likely.
As glyphosate is a systemic herbicide, application should be carried out during periods of active growth, before flowering but late enough to ensure that germinating seedlings have grown up sufficiently to be adequately covered by the herbicide (50+ cm would be suitable).
The initial application should ideally be carried out in May/June with subsequent treatments/monitoring likely being required in July/August and September/October.
Herbicide application could be used as a follow up to hand pulling, e.g. later in the year to deal with any missed plants or regrowth from seed bank.
Due to Himalayan Balsam’s preference for habitats near water, this limits herbicide selection to products approved for use near water and the operatives applying it must be trained to PA6Aw level.
The herbicide can be applied as a spot treatment to individual plants, using hand-held equipment, or as an overall spray using machine-mounted spray booms. In the latter instance, total weed control of all vegetation will occur, increasing the requirement for revegetation.
Where accessibility is problematic, e.g. river banks, a long lance sprayer may be useful.
Herbicide application will not kill seeds in the seed bank and monitoring with follow-up control must be repeated annually over 2-3 years to eradicate new plants growing in subsequent years, though the numbers decrease significantly from one year to the next.

N.B. Removal, or herbicide treatment, of plants that have already shed their seeds is pointless, as the plants will die at the end of the growing season regardless. It is likely, particularly in the first year of control, that new plants will sprout following the initial removal/treatment, either because shade suppression will be reduced or due to soil disturbance. As such, several additional visits will likely be required. Three visits, May/June, July/August and September/October should be sufficient to catch all regrowth, although, a cautionary approach is advisable.
N.B. Plants that germinate after September/October are very unlikely to have sufficient time to complete their life cycle and produce seeds.

Further Resources:

Prevent Spread:

Import only clean soil from known sources
Ensure all vehicles and equipment are cleaned to avoid cross contamination
Be aware of the threat of colonisation from upstream areas washing Himalayan balsam material downstream
Promote native species and biodiversity - use alternative, native plants
Know what you are buying/growing and source native Irish seed and plants
Do not swap plants and cuttings
Never collect plants from the wild
Safe disposal of plant material and growing media.
Report all sightings

BE PLANT WISE!!

Current Legislative Position (Listed on 03 August 2017)

This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.