The alliance Caucalidion includes vegetation of thermophilous annual weeds growing in cereal fields or vineyards on base-rich soils at low altitudes. Its distribution range includes central and southern Europe. Caucalidion communities are often rich in species and contain several endangered species, mostly archaeophytes of Mediterranean or Near East origin. In the past it contained some weed species which were sown with the crop every year, but with the advent of modern seed-cleaning technologies these species rapidly declined. Species composition of Caucalidion vegetation changes remarkably during the season, and therefore separate associations are recognized for spring and summer communities on the same sites.