Impatiens glandulifera | Indian Balsam | Lus na pléisce
Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).
Listed as a schedule 9 species under Articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).
Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].
First reported in the wild
Invasive species - risk of High Impact
Introduction pathways - 1
Escape from Confinement
Introduction pathways subclass - 1
NAPRA Ireland risk assessed
Yes. This species underwent a Non-native species APplication based Risk Analysis in 2014.
Overall risk of this species to Ireland is categorised as: MAJOR with a MEDIUM level of confidence.
Overall conclusion summary: Impatiens glandulifera poses a major risk to native biodiversity, native ecosystems and conservation goals in principally riparian habitats in Ireland. Although it can spread rapidly and establish dense infestations, information on impacts is limited.
Full risk assessment can be accessed from: http://nonnativespecies.ie/wp-content/uploads/2014/03/Impatiens-glandulifera-Himalayan-balsam1.pdf
Annual herb, erect stem up to 2m, flowers deep pink or purple to white, leaves opposite and in whorls of 3, 2.5-4cm (Stace, 1997).
Can cause soil erosion on river banks, as well as affecting downstream, instream communities by the addition of nutrient rich sediment (Greenwood & Kuhn. 2014). Presence of I. glandulifera may decrease plant species richness by 25% (Hulme & Bremner, 2006), as well as promoting the spread of other invasive species, even upon removal, by altering the soil fungal communities (specifically the arbuscular mycorrhizal fungi (AMF)) to the detriment of native species (Tanner & Gange, 2013). Stands of I. glandulifera support a lower diversity of Coleoptera and Heteroptera insect species than similar uninvaded plots (Tanner et al., 2014).
Mires, bogs & fens; Heath, scrubland & tundra; Woodland, forest and other wooded land; Regularly or recently cultivated agricultural, horticultural or domestic habitat
Seed production in I. glandulifera is dependent on plant density, with seed production decreasing with increased plant density but range from 500 - 2500 seeds per plant (Beerling & Perrins, 1993).
Pathway and vector description
Previously popular garden plant promoted by bee keepers (Millane & Caffrey, 2014), in some cases it escaped from cultivation, though it may have been deliberately spread as was the case in the UK (Rotherham, 2000).
Mechanism of impact
There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017).To achieve complete control measures must be implemented on an ongoing basis for several years (EPPO, 2005). When tackling infestations along waterways, in order to avoid reinfestation by seeds travelling downstream, work should start upstream and proceed in a downstream direction (EPPO, 2005).
Very shallow roots mean that this species can be easily hand-pulled but care must be taken to remove all parts of the plant (Helmisaari, 2010). Should be carried out before seed set, usually at the end of July (Helmisaari, 2010). If seeds are already present the heads can be bagged and then cut off before the rest of the plant is removed (Kelly et al., 2008).
Infestations can readily be controlled in accessible areas by mowing/strimming at appearance of first flowers to prevent the setting of seed. Cutting earlier than the start of flowering will encourage shoot regeneration (EPPO, 2005; Helmisaari, 2010; Q-bank, undated). Strimming/mowing should remove the plant below the first node.
Can be controlled by spraying in June with 2,4-D, tricolpyr or glyphosate (EPPO, 2005). Some formulations of glyphosate are approved in Ireland for use near water. Where the plant hasn't achieved complete dominance a weed wiper can be used to apply glyphosate to avoid contacting non-target species (Kelly et al., 2008).
Grazing by livestock can be used to eliminate stands of Impatiens glandulifera where access is possible. (EPPO, 2005; Helmisaari, 2010; Q-bank, undated). This may need to be repeated annually.
Plant material, with the exception of seeds, can be composted. Material contaminated by seeds must be disposed of by 'deep burial' (Department of Agriculture and the Marine, undated).
Areas that have undergone control measures should be monitored for several weeks for any regrowth (EPPO, 2005).
Found on riversides, roadsides, waste ground and former cultivated fields, prefers damp ground (Reynolds, 2002).
Established - Widespread. Locally abundant, naturalised though still spreading, can form dense stands (Reynolds, 2002).
Originally native to the Himalayan mountain region this species has been cultivated in China for centuries and those plants may represent the source of the introduction (Rotherham, 2000).
Date of first record category
Fifty year date category
Records submitted to Data Centre in 2023
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
Report any sightings to the National Biodiversity Data Centre. Do not purchase this plant. Dispose of garden waste responsibly and never plant non-native species in the wild.
Delivering Alien Invasive Species In Europe (DAISIE) project list this as one of the 100 Worst Invaders in Europe.
Beerling, D.J. and Perrins, J.M. (1993) Impatiens glandulifera Royle (Impatiens roylei Walp.). Journal of Ecology, 81, 367-382.
Department of Agriculture, Food and the Marine (Ireland) (undated) Invasive plant information note – Himalayan balsam Impatiens glandulifera. https://www.agriculture.gov.ie/media/migration/farmingschemesandpayments/glastraining/HimalayanBalsamFinalDraft230616.pdf Site accessed 25 September 2017.
European and Mediterranean Plant Protection Organisation (EPPO) (2005) Draft EPPO data sheet on invasive plants – Impatiens glandulifera. EPPO. Paris. https://www.eppo.int/INVASIVE_PLANTS/ias_lists.htm Site accessed 25 September 2017.
European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.
Greenwood, P., & Kuhn, N. J. (2014). Does the invasive plant, Impatiens glandulifera, promote soil erosion along the riparian zone? An investigation on a small watercourse in northwest Switzerland. Journal of Soils and Sediments, 14(3), 637-650.
Helmisaari, H. (2010): NOBANIS – Invasive Alien Species Fact Sheet – Impatiens glandulifera. – From: Online Database of the European Network on Invasive Alien Species – NOBANIS www.nobanis.org Site accessed 25 September 2017.
Hulme P.E & Bremner E.T., 2006. Assessing the impact of Impatiens glandulifera on riparian habitats: partitioning diversity components following species removal. Journal of Applied Ecology, 43, 43-50.
Kelly, J., Maguire, C.M. and Cosgrove, P.J. (2008). Best practice management guidelines Himalayan balsam Impatiens glandulifera. Prepared for NIEA and NPWS as part of Invasive Species Ireland. http://www.nonnativespecies.org/index.cfm?pageid=147 Site accessed 25 September 2017.
Millane, M. & Caffrey, J. (2014). Risk Assessment of Impatiens glandulifera Royle – Himalayan Balsam. Report prepared for Inland Fisheries Ireland and the National Biodiversity Data Centre.
Q-bank (2017) Q-bank factsheet Impatiens glandulifera Royle, Indian Balsam. http://www.q-bank.eu/Plants/Factsheets/Impatiens_glandulifera_EN.pdf Site accessed 25 September 2017.
Reynolds, S.C.P. (2002) A catalogue of alien plants in Ireland. National Botanic Gardens. Glasnevin, Dublin.
Rotherham. I.P. (2000). Exotic Invasive Species – should we be concerned? Himalayan balsam - the human touch. Proceedings of the Institute of Ecology and Environmental Management Conference, Birmingham, April, 2000.
Stace, C. (1997). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge.
Tanner, R. A., Varia, S., Eschen, R., Wood, S., Murphy, S. T., & Gange, A. C. (2013). Impacts of an invasive non-native annual weed, Impatiens glandulifera, on above-and below-ground invertebrate communities in the United Kingdom. PloS one, 8(6), e67271.
Tanner, R. A., & Gange, A. C. (2013). The impact of two non-native plant species on native flora performance: potential implications for habitat restoration. Plant Ecology, 214(3), 423-432.
Global Invasive Species Database