An annual, thoroughly naturalised by rivers, canals and adjacent reservoirs. The seeds can be ejected from its capsules to a distance of a few metres, and can be dispersed by water. Lowland.
Introduced probably in the very early 19th century, the first record of I. capensis outside cultivation was from Surrey in 1822. There has since been a steady expansion into semi-natural habitats, which still continues. The Norfolk population originated from an independent introduction to a tributary of the Bure near Aylsham in 1927 (Petch & Swann, 1968).
Native of North America; also naturalised in France and Germany, although on a smaller scale than in our area.
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.
Atlas text references
Atlas (96b) Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols,
, Königstein, (1986)
Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols,
, Jena, (1978)
The distribution and dispersal of two alien species of Impatiens, waterway weeds in the British Isles,
, Proceedings EWRS / AAB 7th Symposium on Aquatic Weeds 1986, p.351-356, (1986)