A perennial herb thoroughly naturalised on sea-cliffs, limestone rock outcrops and pavements, rocky waste ground, in quarries, on railway banks, on old walls and buildings, and in other well-drained, disturbed and open habitats. Lowland.
C. ruber was grown in Britain by 1597 and is a popular garden plant. It was first recorded in the wild in 1763 (Cambs.). There are many more records for this species than when it was mapped in the 1962 Atlas, although its range has not changed significantly.
Native of S.W. Europe and the Mediterranean region; widely naturalised further north in W. & C. Europe.