This annual of disturbed, usually fertile ground is found on roadsides, waste ground, tracks and in field gateways, and in arable crops. Generally lowland, but reaching 845 m on Great Dun Fell (Westmorland).
Although cultivated in 1781, this species was first recorded in the wild in Britain as an escape from Kew Gardens in 1871 and in Ireland in 1894, and it became one of the fastest spreading plants in the 20th century. Its spread was aided by the transport of seeds on tyres and footwear. The distribution is now stable.
Probably native of N. & S. Asia and perhaps adjacent parts of N. America; in the 19th and 20th centuries it spread to boreal and temperate zones throughout the N. hemisphere.
Light (Ellenberg): 7
Moisture (Ellenberg): 5
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 7
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.6
July Mean Temperature (Celsius): 14.5
Annual Precipitation (mm): 1086
Height (cm): 35
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 2677
Count of 10km squares in Ireland: 945
Count of 10km squares in the Channel Isles: 14
Atlas Change Index: -0.49
Weighted Changed Factor: -19
Weighted Change Factor Confidence (90%)
Atlas text references
1988. Comparative Plant Ecology.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
1992. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 3. 2 vols.
1964. Weeds & Aliens, edn 2.