Cornflower (Centaurea cyanus) is an annual or biennial monoicous herbaceous plant. Mainly grows as noxious weed especially on winter crops fields, but also on road sides, ditches and barren vegetation areas. Prefers sandy soils but grows elsewhere as well. Light-loving cornflower can endure shade. Flowers are primarily blue, but can also be violet blue, in rare cases violet red, purplish pink or even white. Flowers from June to September (October). Cornflower is an excellent harvest plant for honeybees and also a known medicinal herb. The infusion of its flower is used to promote urine and bile excretion, as well as eye compresses. In folk medicine, flowers of spirit or water have been used to remedy cough and fever. The plant is rich in vitamin C.
Since 1968, cornflower has been the national flower of Estonia.
About this stamp in philately foorum.