Cornflowers are annual plants which are famous for the intensely rich blue color of their blossoms. These plants are native to Eurasia, but they are widely cultivated in the Northern Hemisphere, and a number of specialty cultivars have been produced, with flowers in colors like white, pink, and purple in addition to the famous blue. Cornflower blue is so distinctive that it appears as a color in sets of crayons and paints, and people's eyes are sometimes compared to cornflowers.
The most well known cornflower species is probably Centaurea cyanus, although several others are sold as garden plants. Cornflowers produce spear-like leaves and disc-shaped heads of blossoms which do very well as cut and dried flowers in addition to looking attractive in the garden. Depending on where cornflowers are grown, they generally bloom in the late spring and early summer, after which the plant will produce seed and then die back, allowing gardeners to remove it.
The cornflower is extremely hardy, thriving in USDA zones three through 10. In North America, cornflowers are prized as garden flowers, but they also grow wild, thanks to their adaptability. In Eurasia, cornflowers tend to be treated more like weeds in many regions, since they can wreak havoc on crops, and in some areas of its native range the flower has ironically been classified as a threatened species which may vanish, due to vigorous eradication efforts.
There are a number of alternate names for the cornflower, including bachelor's button, bluebonnet, bluebottle, and ragged sailor. The "bachelor's button" comes from a tradition of wearing cornflowers in the buttonhole while courting, since the flowers last a long time as cut flowers; according to legend, if cornflowers faded or wilted in a young man's buttonhole, it suggested that his affections were not genuine.
The cornflower has also been used in traditional herbal medicine, steeped to make a rinse for sore or tired eyes. Cornflowers are also edible; they are traditionally added to some tea blends such as Lady Grey, and they are also used to garnish food or to add a note of color to pitchers of water.
When planting cornflowers in the garden, it helps to cluster them so that they will create a dense mass of blue when they bloom. Some cornflower varieties also get quite tall, making them suitable for use as filler in large beds where a rich background color might be desired.