Centaurea cyanus is also known as cornflower, basketflower, bluebottle, hurtsickcle and more commonly, perhaps, a bachelor button. It is hard to understand how this was considered a weed that filled the fields and thus got the name cornflower, like a grain. Then with agriculture growth and herbicides used to control weeds, it became endangered. It can be found in only 3 sites in England where it used to be in over 250 areas. Yet again, since it "sneaks" into grain seeds that are sent around the world, it is also known as an invasive weed or naturalized flower in other areas around the world!
In the United States they are popular in "grandma's garden." The name bachelor button came about as bachelors wore them in their lapels when they were sweet on someone they wanted to date. The longer the flower lasted, the stronger that the love was true love. If the flower died fairly soon, than the bachelor had to find another true love.
The flowers are edible and look nice in salads. They are also used in Lady Gray teas. When picked, it should be in the early morning while still in bud and they will last longer in the flower arrangements.
My plant came out of a package of "wildflower" seeds that I scattered in a small bed. I have only two little plants, but I do love that true blue color.