Conoclinium coelestinum

Native to southeastern Canada, the central and eastern United States and Cuba, this plant is a perennial herb usually eighteen inches to three feet tall. It spreads through underground rhizomes and self-seeding, forming colonies in moist ground, including ditch banks. The opposite, broadly triangular to oval leaves have coarse teeth and prominent veins. Flat-topped clusters contain many small blue-purple flower heads made entirely of tubular disc florets, without petal-like rays. The long, projecting, two-branched styles give the flowers their fluffy appearance. Flowering extends from late summer into fall. Each small, five-ribbed dry fruit bears a tuft of fine bristles. Photographed in Florida.