An annual of open, sandy, disturbed ground, occurring as a weed in farmland and in gardens, and also under light shade, such as Breckland pine-belts. It is absent from wet and ill-drained soils and from limestone. Lowland.
C. perfoliata was introduced into cultivation in 1794. It was first recorded in the wild in 1849 and by 1853 was the most troublesome weed in the Chelsea Physic Garden (Kent, 1975). However, it was still relatively uncommon up to 1930. Since then it has spread significantly, and still seems to be increasing.
Native of western N. America; widely naturalised in N.W. Europe.
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