A usually annual herb of open habitats in dry grassland, rocky ground or arable fields. In Britain it usually grows on calcareous soils, whereas in Ireland it occurs on sandy and gravelly sites, including eskers. It is also a rare casual of waste ground, quarries and banks by roads and railways. Lowland.
C. acinos has substantially declined as a result of more efficient methods of weed control and, in Ireland, gravel extraction. In many areas it is no longer found in arable fields, surviving only in less intensively managed habitats. It is considered to be alien in Ireland (Scannell & Synnott, 1987).
European Temperate element; also in C. Asia.