An annual weed of arable land and waste ground. It is sometimes an abundant or even pernicious weed on light, sandy soils. It arises as a contaminant of grain and from wool shoddy. Lowland.
A. micrantha was first cultivated in Britain in 1836, but was not recorded from the wild until later, in 1910, when it was introduced as a seed impurity. It has increased steadily since the 1950s, and is clearly much more frequent now than formerly. It has been confused with A. lycopsoides.
Native of western N. America.
Light (Ellenberg): 9
Moisture (Ellenberg): 3
Reaction (Ellenberg): 3
Nitrogen (Ellenberg): 3
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.4
July Mean Temperature (Celsius): 15.4
Annual Precipitation (mm): 701
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.