Himalayan Balsam

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iHimalayan Balsam

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Scientific classification

Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Ericales
Family:	Balsaminaceae
Genus:	Impatiens
Species:	I. glandulifera

Binomial name

Impatiens glandulifera
Royle

Himalayan Balsam (Impatiens glandulifera) is a large annual plant, native to the Himalaya. It typically grows to 1 to 2 meters high, with a soft green or red-tinged stem, and lanceolate leaves 5–23 cm long. The crushed foliage has a strong musty smell. The flowers are pink, with a hooded shape, 3–4 cm tall and 2 cm broad; the flower shape has been compared to a policeman's helmet, giving rise to the alternative common name "policeman's helmet".

Leaves of the Himalayan Balsam

After flowering between June and October, the plant forms seed pods 2–3 cm long and 8 mm broad, which explode when disturbed, scattering the seeds up to 7 metres. Impatiens, meaning "impatient", refers to this method of dispersal.

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 weed. The aggressive seed dispersal, coupled with high nectar production which attracts pollinaters, often allows the Himalayan Balsam to outcompete native plants. In the UK, some local wildlife trusts organise "balsam bashing" events to help control the plant.

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 neophytes 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 decrese eutrophication, thereby permitting the better-adapted local vegetation that gets outgrown by the balsam on watercourses with high nutrient load to rebound naturally. Regarding stands of the plant at forest edges and meadow habitats, they caution that these conclusions do probably not hold true; in such localities, manual destruction is apparently still the best way to stem or slow the expansion of Himalayan Balm.

[edit] References

Hejda, Martin & Pyšek, Petr (2006): What is the impact of Impatiens glandulifera on species diversity of invaded riparian vegetation? Biological Conservation 132(2): 143-152. DOI:10.1016/j.biocon.2006.03.025 (HTML abstract)