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Genus Cosmos

Cosmos Cosmos bipinnatus 'Sea Shells' Photo/Illustration: Susan Roth
KOZ-mose
Typical for Cosmos are cup or bowl-shaped flowers in colorful shades of orange, pink, red, white, and maroon. They are ideal for a cutting garden, mixed border, or annual border. The copious flowers are set atop stiff stems and thread-like foliage.
 Noteworthy characteristics: These plants are found in scrub and meadows of the southern U.S. and Central America. They are loved by butterflies, and make excellent cut flowers. The plants are moderately drought and heat tolerant.
 Care: Grow in moderately fertile, moist but well-drained soil in full sun. Deadhead to prolong flowering, and also leave some seeds to self sow. In cold climates, lift the tubers of tender perennial species and store in a frost-free location. 
 Propagation: Sow seed in situ in late spring or at 61°F in mid-spring.
 Problems: Stem canker, powdery mildew, Rhizoctonia stem rot, gray mold, aphids.

Species, varieties and cultivars for genus Cosmos

Cosmos atrosanguineus Cosmos atrosanguineus
(Chocolate cosmos, Black cosmos) (3 user reviews)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

A chocolate scented flower! Dark red-brown, sometimes almost black, velvety flowers on long, slender, reddish brown stems bloom from early summer to autumn. Chocolate cosmos is a tuberous-rooted, tender perennial native to Mexico that can be overwintered indoors where not hardy. Grow in a border or in containers where the flowers can be appreciated up close. They also make good cut flowers.
Cosmos bipinnatus 'Sea Shells' Cosmos bipinnatus 'Sea Shells'
 (1 user review)

This unique annual produces quilled blossoms of hollow, tube-shaped petals that radiate from the center in shades of white, pink, or carmine red. The flowers, which bloom all summer long, sometimes have bicolored interior and exterior tubes. 
Cosmos bipinnatus 'Sensation Series' Cosmos bipinnatus 'Sensation Series'
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This series of annuals produces extra large, cup-shaped blossoms to 3-1/2 inches across in shades of white or pink all summer long. 
Cosmos bipinnatus 'Sonata Dwarf Mix' Cosmos bipinnatus 'Sonata Dwarf Mix'
 (1 user review)

This series produces compact plants 1 foot tall and about as wide with large blossoms in pure white and many shades of pink. These season-long performers make fine edging plants.
Cosmos bipinnatus cvs. Cosmos bipinnatus cvs.
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Cosmos are branching annuals with ferny foliage and pink, crimson, or white flowers that work well in the back of a border. Although introduced in 1799, cosmos did not beome popular for the garden or as the subject of breeding efforts until the early 1900s. The rest is now history. The variety 'Sensation' won the All-American Selection Award of Merit in 1936 for its clear colors of pink and white, on early-blooming, 3- to 4-foot-tall plants. 'Purity' is the glistening white form of cosmos in the 'Sensation' series. 'Sea Shells' has quilled florets. The Sonata Series cultivars are dwarf plants only growing to about a foot or two tall.
Cosmos sulfureus 'Cosmic Red' Cosmos sulfureus 'Cosmic Red'
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The intense scarlet red blooms and yellow centers of this bedding plant will stop you in your tracks. ‘Cosmic Red’ blooms all summer and looks great at the front of the border and in containers. As with other cosmos cultivars, grow this plant in full sun and moist, well-drained soil. The already hypnotic color will intensify as light levels increase.