Impatiens glandulifera

"Policeman's helmet" redirects here. For the uniform cover, see Custodian helmet.
Impatiens glandulifera
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Ericales
Family: Balsaminaceae
Genus: Impatiens
Species: I. glandulifera
Binomial name
Impatiens glandulifera
Royle
Synonyms[1]

Impatiens glandulifera is a large annual plant native to the Himalayas.[2] Via human introduction it is now present across much of the Northern Hemisphere and considered an invasive species in some areas.

Etymology

The common names Policeman's Helmet, Bobby Tops, Copper Tops, and Gnome's Hatstand all originate from the flowers being decidedly hat-shaped. Himalayan Balsam and Kiss-me-on-the-mountain arise from the plant originating in the Himalayan mountains. Ornamental jewelweed refers to its cultivation as an ornamental plant.

The genus name Impatiens, meaning "impatient", refers to its method of seed dispersal. The species name glandulifera comes from the Latin words glandis meaning 'gland', and ferre meaning 'to bear', referring to the plant's glands.

Description

Impatiens glandulifera scattering its seeds
Leaves of the Himalayan Balsam
Glands

It typically grows to 1 to 2 m (3.3 to 6.6 ft) high, with a soft green or red-tinged stem, and lanceolate leaves 5 to 23 cm (2.0 to 9.1 in) long. The crushed foliage has a strong musty smell. Below the leaf stems the plant has glands that produce a sticky, sweet-smelling, and edible nectar. The flowers are pink, with a hooded shape, 3 to 4 cm (1¼ to 1½ in) tall and 2 cm (¾ in) broad; the flower shape has been compared to a policeman's helmet.

After flowering between June and October, the plant forms seed pods 2 to 3 cm (¾ to 1¼ in) long and 8 mm broad (¼ in), which explode when disturbed,[3] scattering the seeds up to 7 metres (23 feet).

The green seed pods, seeds, young leaves and shoots are all edible. The flowers can be turned into a jam or parfait.[4]

Distribution

Ireland

Recorded from almost all counties of Ireland.[5][6]

Invasive species

Himalayan Balsam is sometimes cultivated for its flowers. It is now widely established in other parts of the world (such as the British Isles and the United States), in some cases becoming an invasive species weed. The aggressive seed dispersal, coupled with high nectar production which attracts pollinators, often allows the Himalayan Balsam to outcompete native plants. Himalayan Balsam also promotes river bank erosion due to the plant dying back over winter, leaving the bank unprotected from flooding.[7] Invasive Himalayan Balsam can also adversely affect indigenous species by attracting pollinators (e.g. insects) at the expense of indigenous species.[8] It is considered a "prohibited noxious weed" under the Alberta Weed Control Act 2010.[9]

In the UK the plant was first introduced in 1839 at the same time as Giant Hogweed and Japanese Knotweed.[10][11] These plants were all promoted at the time as having the virtues of "herculean proportions" and "splendid invasiveness" which meant that ordinary people could buy them for the cost of a packet of seeds to rival the expensive orchids grown in the greenhouses of the rich. Within ten years, however, Himalayan balsam had escaped from the confines of cultivation and begun to spread along the river systems of England.[10] Today it has spread across most of the UK and some local wildlife trusts organise "balsam bashing" events to help control the plant.[10] However, a recent study (Hejda & Pyšek, 2006) concludes that in some circumstances, such efforts may cause more harm than good. Destroying riparian stands of Himalayan Balsam can open up the habitat for more aggressive invasive plants such as Japanese knotweed and aid in seed dispersal (by dropped seeds sticking to shoes). Riparian habitat is suboptimal for I. glandulifera, and spring or autumn flooding destroys seeds and plants. The research suggests that the optimal way to control the spread of riparian Himalayan Balsam is to decrease eutrophication, thereby permitting the better-adapted local vegetation that gets outgrown by the balsam on watercourses with high nutrient load to rebound naturally. They caution that these conclusions do probably not hold true for stands of the plant at forest edges and meadow habitats, where manual destruction is still the best approach.

Himalayan Balsam at Bank Hall, Bretherton, Lancashire, England

The Bionic Control of Invasive Weeds in Wiesbaden, Germany, is trying to establish a self-sufficient project to conserve their local biodiversity by developing several food products made from the Impatiens flowers. Eventually, if all goes well, this project will have the Himalayan Balsam financing its own eradication.

In August 2014, CABI released a rust fungus in Berkshire, Cornwall and Middlesex in the United Kingdom as part of field trials into the biological control of Himalayan Balsam.[12]

Some research also suggests that I. glandulifera may exhibit allelopathy, in which it excretes toxins that negatively affect neighboring plants, thus increasing its competitive advantage.[13] This would further support the conclusion that pulling or cutting the plant and leaving it to decompose is not the best method to control this invasive species.

The Royal Horticultural Society and the Centre for Ecology and Hydrology recommend that pulling and cutting is the main method of non-chemical control, and usually the most appropriate.[14][15] Natural Resources Wales has used manual methods such as pulling plants and using strimmers to largely eradicate Himalayan Balsam from reaches of the River Ystwyth.[16]

Fruits of impatiens glandulifera

References

  1. ↑ "The Plant List: A Working List of All Plant Species". Retrieved 7 April 2014.
  2. ↑ Webb, D.A., Parnell, J. and Doogue, D. 1996. An Irish Flora. Dundalgan Press (W.Tempest) Ltd. Dundalk
  3. ↑ Scott, R. 2004. Wild Belfast on safari in the city. Blackstaff Press. ISBN 0 85640 762 3
  4. ↑ "Gastronomie: Springkraut & Co.: Kräuterkoch Peter Becker macht aus Neophyten Salat". Badische Zeitung. 13 September 2011. Retrieved 21 May 2015.
  5. ↑ Scannell, M.J.P. and Synnott, D.M. 1972. Census Catalogue of the Flora of Ireland. Dublin. Published by the Stationery Office.
  6. ↑ Hackney, P. (Ed)1992. Stewart & Corry's Flora of the North-East of Ireland. The Institute of Irish Studies, The Queen's University of Belfast. ISBN 0 85389 446 9
  7. ↑ Greenwood, Phillip; Fister, Wolfgang; Kuhn, Nikolas (2014). "The potential influence of the invasive plant, Impatiens glandulifera (Himalayan Balsam), on the ecohydromorphic functioning of inland river systems" (PDF). Geophysical Research Abstracts. Retrieved 14 May 2015.
  8. ↑ "The influence of an invasive plant species on the pollination success and reproductive output of three riparian plant species". Biological Invasions. Springer. 14 (2): 355–365. 30 July 2011. doi:10.1007/s10530-011-0067-y. Retrieved 14 May 2015.
  9. ↑ "Alberta Invasive Plant Identification Guide" (PDF). Wheatland County, Alberta. 2012. Retrieved 9 June 2013.
  10. 1 2 3 Mabey, Richard (25 July 2011). "Indian Balsam". Mabey in the wild. BBC. Retrieved 24 July 2011.
  11. ↑ "Wanted!: Himalayan Balsam". British Isles: A Natural History. The Open University. Retrieved 4 December 2009.
  12. ↑ "CABI releases rust fungus to control invasive weed, Himalayan balsam". cabi.org. CABI. 26 August 2014. Retrieved 17 May 2015.
  13. ↑ http://www.aka.fi/Tiedostot/Viksu/2012ty%C3%B6t/Sofia%20Mononen%20kilpailuty%C3%B6.pdf
  14. ↑ "Himalayan Balsam". Royal Horticultural Society. Retrieved 2 June 2014.
  15. ↑ "Information Sheet 3: Himalayan Balsam" (PDF). Centre for Ecology and Hydrology: Centre for Aquatic Plant Management. Retrieved 2 June 2014.
  16. ↑ "Cyfoeth Issue 3 September 2013" (PDF). Natural Resources Wales. p. 6. Retrieved 12 June 2015.
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