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Cosmos bipinnatus (photo courtesy of Laura Dunkin-Hubby)
Cosmos bipinnatus (photo courtesy of Laura Dunkin-Hubby)

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Zone
Zones A1-A3, 1-45, H1, H2
Full Sun
Full
Regular Water
Moderate

Cosmos

Asteraceae (Compositae)
Annuals, Perennials, Flowers

Native to tropical America (mostly Mexico). Showy summer- and fall-blooming plants, open and branching in habit, with bright green divided leaves and daisylike flowers in many colors and forms (single, double, crested, and frilled). Heights vary from 2 1/2 to 8 ft. Use for mass color in borders or background, or as filler among shrubs. Useful in arrangements if flowers are cut just after they open and placed immediately in deep, cool water.

Sow seeds in open ground where plants are to grow or set out transplants from spring to summer. Plant in not-too-rich soil. Plants self-sow freely and are attractive to birds.

Cosmos atrosanguineus (photo courtesy of Skagit Gardens)
Cosmos atrosanguineus (photo courtesy of Skagit Gardens)

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Cosmos atrosanguineus

Perennial from tuberous roots. Grows as a perennial in Zones 4–9, 14–24. Where winters are cold, dig and store as for dahlias. Grows to 2–2 1/2 ft. tall and 1 1/2 ft. wide, with coarsely cut foliage.

Blooms in late summer and fall, with deep brownish red, nearly 2-in.-wide flowers with a strong perfume of chocolate (some people detect a hint of vanilla as well). An attractive companion for silvery-foliaged plants.

Provide well-drained soil. Winter mulch is prudent in all but the mildest regions (where plant tends to be rather short-lived).

Cosmos bipinnatus ‘Sonata Mix’ (photo courtesy of Linda Lamb Peters)
Cosmos bipinnatus ‘Sonata Mix’ (photo courtesy of Linda Lamb Peters)

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Cosmos bipinnatus

Annual in heights up to 8 ft. and widths to 1 1/2–2 1/2 ft. Blossoms are 3–4 in. wide, with tufted yellow centers and rays in white and shades of pink, rose, lavender, purple, or crimson. Attracts bees and beneficial insects. 

Among the many types are 3–4-ft.-tall ‘Candystripe’, with white-and-rose flowers; Doubleclick strain, to 4 ft. tall with frilly, double flowers in a range of colors; ‘Picotee’, to 2 1/2 ft. tall with white flowers edged in red; Sensation strain, 3–6 ft. tall, including ‘Dazzler’ (crimson) and ‘Radiance’ (rose with red center); and ‘Sea Shells’, to 3 ft. tall, grown for quilled ray flowers that look like long, slender cones. Sonata is a dwarf strain 1 1/2–2 ft. tall; ‘Sweet Dreams’ reaches 3 ft. tall and has pale pink to white blossoms with rose centers; Versailles strain, bred for cut flowers, reaches 3 1/2 ft. tall and bears its blossoms on long, strong stems. 

Cosmos sulphureus (photo courtesy of Annie’s Annuals & Perennials)
Cosmos sulphureus (photo courtesy of Annie’s Annuals & Perennials)

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Cosmos sulphureus

This annual grows to 7 ft. tall and 1 1/2–2 1/2 ft. wide, with yellow-centered, yellow or orange-yellow single flowers. Tends to become weedy-looking at the end of the season. Two 3–4-ft.-tall, semidouble-flowering strains are Bright Lights, with 3 1/2-in. flowers in yellow, gold, orange, and orange-red; and Klondike, with 2-in. flowers ranging from scarlet-orange to yellow. Dwarf Klondike or Sunny strain is 1 1/2 ft. tall, bears 1 1/2-in. flowers. Foot-tall semidouble bloomers include Ladybird mix, with 2 1/2-in. scarlet, yellow, and orange flowers; and ‘Sunny Red’, with orange-red blooms. ‘Yellow Garden’ grows to 3 ft. tall and wide, bears light yellow blooms with white center and edge.

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