An annual of damp mud on the margins of ponds and lakes, canals, rivers and streams, or shallow depressions such as vehicle tracks and hoof-marks in woodland rides, around field gateways and in wet meadows. It is almost invariably in sites which are waterlogged in winter, often on base-poor soils and sometimes in partial shade. 0-505 m (Llyn Crugnant, Cards.).
The distribution of P. hydropiper has not changed markedly since the 1962 Atlas, although there have been losses at the eastern edge of its range.
Circumpolar Temperate element; widely naturalised outside its native range.
Light (Ellenberg): 7
Moisture (Ellenberg): 7
Reaction (Ellenberg): 6
Nitrogen (Ellenberg): 6
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.7
July Mean Temperature (Celsius): 14.8
Annual Precipitation (mm): 1093
Height (cm): 75
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 2041
Count of 10km squares in Ireland: 740
Count of 10km squares in the Channel Isles: 9
Atlas Change Index: -0.41
Weighted Changed Factor: -3
Weighted Change Factor Confidence (90%)
Atlas text references
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1979)
1981. Docks and knotweeds of the British Isles. Botanical Society of the British Isles Handbook no. 3.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1966. Biological Flora of the British Isles. No. 103. Polygonum hydropiper L. Journal of Ecology. 54:815-821.