Cosmos (C. bipinnatus) must be one of the easiest annuals ever. Sow its seeds once, and pink or white flowers come back year after year from their own seeds.
Flowers (mostly singles) start blooming in early summer and continue for months until the first hard frost. The wonderful Sensation strain is the best known of the clan, but cosmos come in many other flower forms―some have rolled or frilled petals―and in a range of solid colors and stripes.
OUR FAVORITES: 'Candy Stripe' produces white flowers with crimson borders or stripes and grows to 3 to 31/2 feet tall. Three-foot-tall 'Daydream' has petals of rosy pink that fade to pale pink edges. Psyche mix bears semidouble blooms and grows to 3 feet tall. Seashell mix (to 31/2 ft. tall) has rolled petals in creamy white and shades of red, rose, and pale seashell pink. Sonata mix, a 2-foot dwarf, bears many 3-inch single blooms in white, pink, and mixes. 'Versailles Tetra' (to 3 ft. tall) has 4-inch pink flowers and darker shading around a bright yellow eye.