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Glabrous annual herb with stout succulent, reddish-translucent hollow stems to 2.5 m; leaves opposite or in whorls of 3, 5-18 cm long and 3-7 cm wide; flowers with short spur, helmeted upper petal, deep purplish-pink to white, strong balsam smell.
Well established and extremely invasive throughout most of lowland Great Britain.
Moist and semi-shaded damp places, predominant on banksides by slow-moving watercourses.
|Native range:||Indian Subcontinent|
|Functional type:||Land plant|
|Status in England:||Non-Native|
|Status in Scotland:||Non-Native|
|Status in Wales:||Non-Native|
|Location of first record:||v.c.21|
|Date of first record:||1855|
Native to the western and central Himalaya.
First introduced in 1839. First records of naturalisation were Hertfordshire and Middlesex in 1855.
Introduced to Kew Gardens by Dr Royle from Kashmir. Floating seeds can travel long distances before becoming lodged and germinating in a soft muddy bankside. However, the most widespread distribution has been by human means where individuals pass on seed to others.
It is a major weed problem, especially on riverbanks and waste land, but can also invade gardens. It grows rapidly and spreads quickly. The plant is widespread throughout northern and eastern Europe and central Scandinavia, where it has reached pest status in many countries. It is also classified as a noxious weed in 3 US States. It is listed on Schedule 9 of the Wildlife and Countryside Act 1981 with respect to England and Wales, which makes it an offence to plant it or introduce it to the wild.
At ripening, explosive dehiscence of the fruit capsule; each plant ejecting as many as 800 seeds for a distance of up to 7 m.
Germination occurs in February-March, followed by rapid shoot extension and leaf expansion from April. Plants flower from July to October, setting seed from mid-July onwards. Onset of flowering can be delayed by 2-3 weeks in shaded sites.
In GB, sheep and cattle are known to graze the leaves, stems and flowers indiscriminately. Two species of aphid are known to feed on the plant. It is also a recognised food plant of the Elephant Hawk-moth.
Most seeds overwinter for one season before germinating the following spring; however, there is some evidence of a persistant seedbank lasting for at least 2 years.
Moist and semi-shaded places, waste ground, thin woodlands; but particularly on soft banks by slow-moving water along canalsides, streams and rivers.
Widespread distribution across most of lowland England and Wales and many parts of Scotland and Ireland. It now occurs in the Channel Islands and at least 108 of the 112 vice-counties in over 2000 10 km (hectad) squares.
Shades out and crowds out many native species, and produces much nectar and therefore attractive to pollinating insects, possibly to the detriment of native flowering plants.
Has the ability to completely change the appearance of riverbanks with its large showy, highly attractive and pungent flowers. Not known to be poisonous, but has a bitter taste if ingested.
Having become dominant in its invaded habitat, the shallow root system can promote erosion during the annual cycle through dieback and subsequent destruction of bankside structure. Dense stands can impede water flow at times of high rainfall, thereby increasing the likelihood of flooding.
Garrard, I. & Streeter, D. (1998) The wild flowers of the British Isles. Midsummer Books Ltd., London.
Stace, C.A. (2010) New flora of the British Isles, Third Edition, Cambridge University Press, Cambridge.
Beerling, D. J. & Perrins, J. M. (1993) Biological Flora of the British Isles: Impatiens glandulifera Royle (Impatiens roylei Walp.), Journal of Ecology, 81, 367-382.
Perrins, J., Fitter, A. & Williamson, M. (1993) Population biology and rates of invasion of three introduced Impatiens species in the British Isles, Journal of Biogeography, 20, 33-44.
Pyšek, P. (1995) Invasion dynamics of Impatiens glandulifera - a century of spreading reconstructed, Biological Conservation, 74, 41-48.
Perrins, J., Fitter, A. & Williamson, M. (1990) What makes Impatiens glandulifera invasive? In: Palmer, J. (ed.) The biology and control of invasive plants. British Ecological Society Symposium, University of Wales. September 20-21 1990, pp. 8-33.
Preston, C.D., Pearman, D.A. & Dines, T.D. (2002) New Atlas of the British and Irish Flora, Oxford University Press, Oxford.
GB Distribution from NBN Gateway
November 27th 2015
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