Bachelor's Buttons are often referred to as cornflowers. This is because they first grew, like poppies, as weeds in European grain fields. In England, the name for grain is "corn" and what we call corn is known as maize. Cornflowers migrated from the fields into English gardens in the 1600's.
The flowering period is short for these self seeding annuals- about 3-4 weeks or maybe a bit more if they are deadheaded, but their blue flowers are treasured by gardeners. There are also whites and pinks. Seed packages usually contain a mixture.
The plants are drought tolerant and grow in average soil to a height of 36 inches, though there are also dwarf varieties. They belong to the genus Centaurea. Cicely Mary Barker's Song of the Cornflower Fairy describes their domestication:
Mid scarlet of poppies and gold of the corn,
In wide-spreading fields were the cornflowers born;
But now I look round me, and what do I see?
That lilies and roses are now neighbors to me!
There's a beautiful lawn, there are borders and beds,
Where all kinds of flowers raise delicate heads;
For this is a garden, and here, a Boy Blue,
I live and am merry the whole summer through.
My blue is the blue that I always have worn,
And still I remember the poppies and corn.