Himalayan balsam (Impatiens glandulifera)

Also known as: bee-bums, Indian balsam, policeman's helmet, poor-man's orchid, stinky-pops
GenusImpatiens (1)
SizeHeight: up to 250 cm (2)
Leaf width: 3 - 7 cm (2)
Leaf length: 5 - 18 cm (2)
Root length: 15 - 20 cm (3)
Top facts

The Himalayan balsam has yet to be classified by the IUCN.

The Himalayan balsam (Impatiens glandulifera) is an erect, annual plant (4), with large, oblong leaves which have sharply serrated edges (3) (4) (5). The reddish stems of the Himalayan balsam are translucent and succulent (2) (4). The leaves are also succulent and may be arranged opposite each other or in whorls of three (2) (3) (4) (5) (6).

The flowers of the Himalayan balsam can vary between white, pink and purple (5), with colouration differing among individuals within the same habitat (3). The flower has five petals and is said to look like an English policeman’s hat. The petals may or may not be fused together (5), and grow in racemes of between 5 and 12 individual flowers (4). The fruit capsules are green and contain many spherical seeds, which may be green or brown, eventually becoming black when they are mature (3).

The Himalayan balsam is native to the Himalayas in India and Pakistan (2) (3) (4), where it can be found up to elevations of 2,500 metres (3). It has widespread introduced populations throughout Europe, including the United Kingdom, Poland, southern Russia, the Czech Republic, Austria, Slovakia and southern Sweden (3), as well as in parts of North America (4).

In its native habitat, the Himalayan balsam is found in deciduous and mixed forests in slightly shaded or open wet areas. Where it has been introduced, the Himalayan balsam is associated with riparian habitats (3) and other moist and semi-shaded areas (2), although it grows in a wide range of soils and habitat types (3) (5). In its introduced range, this species mainly colonises areas where there has been a moderate level of disturbance, for example where trees have uprooted (3).

The annual reproduction of the Himalayan balsam occurs in the summer, when the flowers are pollinated by insects. The insects may transfer pollen between flowers of conspecifics or from the same plant. The large amount of nectar produced by this species attracts a multitude of pollinators, including bees, wasps and moths. In an ideal environment, a single plant can produce up to 2,500 seeds, which are enclosed in capsules (3). Once mature, these capsules explode when touched (3) (5), throwing the seeds up to seven metres from the parent plant (2) (3) (5). The seeds are also distributed by animals and along water courses (3), although purposeful human dispersal is the main reason for the Himalayan balsam’s widespread distribution. A high proportion of seeds will be dormant throughout the winter, before germinating in spring (2). An abrupt seasonal temperature change usually determines when a seed breaks its dormancy and begins to germinate (3).

After germinating, the seedling has a period of rapid growth and begins to flower between July and October, although this is dependent on the amount of shade in the area (2). Flowering usually begins in July and may continue into October in certain areas (2) (3) (4) (6). Over winter, the mature Himalayan balsam plants decay, which gives the seedlings the chance to become established (3).

Where it has been introduced, the Himalayan balsam often produces more nectar than many of the native species, making its flowers more attractive to pollinating insects than those of other plants living in close proximity (3) (5). It also outcompetes native species for light and space (2), as its large size and high rate of reproduction facilitates rapid colonisation (3) (5). The rapid growth of this species can be extremely problematic around water systems, where it can increase the rate of erosion and obstruct water flow, subsequently increasing the risk of flooding (2) (5).

The Himalayan balsam is listed on Schedule 9 of the Wildlife and Countryside Act 1981 in the United Kingdom, which makes it an offence to plant this species or introduce it into the wild. It is also classed as a noxious weed in three states in the United States (2).

Eradication methods are currently being researched and implemented throughout the non-native range of the Himalayan balsam. Manual removal of the plant and roots seems to be the most effective method, although this is extremely expensive and time consuming. Another method of removal involves using the herbicide glyphosate. However, this may have detrimental ecological effects on the habitat and other flora and fauna, especially for populations living close to water systems (3).

Further research is required into control methods for this troublesome invasive species (3).

Find out more about the Himalayan balsam as an invasive species:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:

  1. Integrated Taxonomic Information System (ITIS) (October, 2013)
  2. GB Non-native Species Secretariat (NNSS): Factsheet - Himalayan balsam (October, 2013)
  3. Clements, D.R., Feenstra, K.R., Jones, K. and Staniforth, R. (2007) The Biology of Invasive Alien Plants in Canada. 9. Impatiens glandulifera Royle. Canadian Journal of Plant Science, 88(2): 403-417.
  4. Hickey, M. and King, C. (1988) 100 Families of Flowering Plants. Cambridge University Press, Cambridge.
  5. Kaufman, S.R. and Kaufman, W. (2012) Invasive Species:Guide to Identification and the Impacts and Control of Common North American Species. Stackpole Books, Pennsylvania.
  6. Flora of Pakistan - Impatiens glandulifera (October, 2013)