Centaurea cyanus

Centaurea cyanus, commonly known as cornflower, is an annual flowering plant in the family Asteraceae, native to Europe. In the past it often grew as a weed in cornfields (in the broad sense of the word "corn", referring to grains, such as wheat, barley, rye, or oats), hence its name. It is now endangered in its native habitat by agricultural intensification, particularly over-use of herbicides, destroying its habitat; in the United Kingdom it has declined from 264 sites to just 3 sites in the last 50 years. In reaction to this, the conservation charity Plantlife named it as one of 101 species it would actively work to bring 'Back from the Brink'. 



It is also, however, through introduction as an ornamental plant in gardens and a seed contaminant in crop seeds, now naturalised in many other parts of the world, including North America and parts of Australia.

Cornflower is an annual plant growing to 16-35 inches tall, with grey-green branched stems. The leaves are lanceolate, 1–4 cm long. The flowers are most commonly an intense blue colour, produced in flowerheads (capitula) 1.5–3 cm diameter, with a ring of a few large, spreading ray florets surrounding a central cluster of disc florets. The blue pigment is protocyanin, which in roses is red. It flowers all summer.

It is grown as an ornamental plant in gardens, where several cultivars have been selected with varying pastel colours, including pink and purple. Cornflower is also grown for the cutflower industry in Canada for use by florists. The most common colour variety for this use is a doubled blue variety such as 'Blue Boy' or 'Blue Diadem'. White, pink, lavender and black (actually a very dark maroon) are also used but less commonly. A relative, Centaurea montana, is a perennial plant which is also cultivated as a garden plant. Cornflowers germinate quickly after planting.


Light requirements: full sun. Water requirements: high-average water daily. Soil pH requirements: neutral (6.6-7.5) to mildly alkaline (7.6-7.8).