Centaurea cyanus. Heirloom strain of pure double blue cornflowers, or bachelor's buttons. Seedheads each contain multiple seeds and can be strewn to grow like wildflowers. Flowers are long stemmed, edible, and easy to grow. They sometimes naturalize.
Organic Double Blue Cornflower Seeds
These were grown in among our French intensive beds of vegetables to attract beneficial insects into the garden. Plants will grow to about 2 ft high and should be spaced about 1 ft apart.