Agrostemma githago, the common corn-cockle (also written "corncockle" and "corn cockle" and known locally simply as "the corncockle").
It grows with a stem to 100 cm long with lanceolate leaves. The flowers are up to 5 cm in diameter, usually single at the ends of the stem. The sepals have 5 narrow teeth much longer than the petals. It has 10 stamens. It has slender pink flowers. It is a stiffly erect plant up to 1 metre (3 feet 3 inches) tall and covered with fine hairs. Its few branches are each tipped with a single deep pink to purple flower. The flowers are scentless, are 25-50 millimetres (0.98-1.97 inches) across and are produced in the summer months - May to September in the northern hemisphere, November to March in the southern hemisphere.
Each petal bears two or three discontinuous black lines. The five narrow pointed sepals exceed the petals and are joined at the base to form a rigid tube with 10 ribs. Leaves are pale green, opposite, narrowly lanceolate, held nearly erect against stem and are 45-145 mm (1.8-5.7 in) long. Seeds are produced in a many-seeded capsule. It can be found in fields, roadsides, railway lines, waste places, and other disturbed areas.
Of European wheat fields. In the 19th century, it was reported as a very common weed of wheat fields and its seeds were inadvertently included in harvested wheat seed and then resown the following season. It is very likely that until the 20th century, most wheat contained some corncockle seed.
It is now present in many parts of the temperate world as an alien species, probably introduced with imported European wheat. It is known to occur throughout much of the United States and parts of Canada, parts of Australia and New Zealand.
In parts of Europe, intensive mechanised farming has put the plant at risk and it is now uncommon or locally distributed. This is partly due to increased use of herbicides, but probably much more to do with changing patterns of agriculture with most wheat now sown in the autumn as winter wheat and then harvested before any corncockle would have flowered or set seed. The plant was believed to be completely extinct in the United Kingdom until 2014, when a single specimen was found growing in Sunderland by an assistant ranger of the National Trust.
It can be found in fields, roadsides, railway lines, waste places, and other disturbed areas.
All parts of the plant are poisonous (githagin, agrostemmic acid). It has been used in folk medicine despite the risk of fatal poisoning.