Sub-category: Aster family
It is an annual plant growing to 40 to 89 cm inches tall, with grey-green branched stems. The leaves are lanceolate, 1 to 4 cm long. The flowers are most commonly an intense blue color, produced in flowerheads (capitula) 1.5 to 3 cm diameter, with a ring of a few large, spreading ray florets surrounding a central cluster of disc florets.
In the past it often grew as a weed in crop fields, hence its name. More commonly it is found as an ornamental plant in flower gardens. It flowers all summer.