Centaurea cyanus

Plants are 20 to 70 cm tall and white-felted, with linear-lanceolate leaves; the lower leaves are usually dried up by flowering time.

Flower heads are solitary, with green bracts bearing a black fringed appendage; the florets are blue and the outer ones strongly enlarged.

Info Flora gives June to October as the flowering period in Switzerland.

The Czech Pladias database gives June to August as the flowering period and records insect pollination.

In Switzerland it grows in cereal fields and on waste ground from the colline to the montane, occasionally subalpine, zone.

In a UK study of sown urban meadows, cornflower produced the most nectar sugar of any annual, about 896 micrograms per floral unit in 24 hours.

In the same study cornflower made the greatest single contribution to the nectar of the annual meadows, about a third of the total.

The Celle bee institute names Kornblumenhonig (cornflower honey) as an example of a varietal honey, which must come wholly or mainly from the named plant.

The Celle bee institute lists cornflower among bee-friendly flowers suitable for almost any garden.

According to a species sheet by Bischoff and Schönhofer published by Agrarumwelt Rheinland-Pfalz, cornflower was introduced about 7000 years ago together with arable farming; Info Flora gives its origin as the eastern Mediterranean.

In Switzerland cornflower is classed as near threatened (NT) on the national Red List.

German direct-payment rules list Centaurea cyanus among the pollen- and nectar-rich species allowed on fallow land used for honey plants.