Growing Guide
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Cosmos (C. bipinnatus)

Annual Flower

Also known as Mexican Aster, Cut Leaf Cosmos
Cosmos bipinnatus
Asteraceae Family

A tall annual that fills space rapidly, Cosmos is renowned for its profuse blooms and generous self-seeding habit. Perfect for providing large splashes of pastel color in the garden.

Site Characteristics
  • full sun
  • part shade

Soil conditions:

  • requires well-drained soil
  • tolerates low fertility
Does not do well in rich soil, becoming leggy and weak. Prefers neutral to alkaline pH and warm weather.
Plant Traits

Lifecycle: annual

Ease-of-care: easy

Height: 1 to 6 feet

Spread: 1 to 2 feet

Bloom time:

  • mid-summer
  • late summer
  • early fall
  • mid-fall

Flowers from July until frost.

Flower color:

  • red
  • violet
  • white
  • pink

Hybrids are available in many different shades of these basic colors, mostly pastels.

Foliage color: medium green

Foliage texture: fine

Very lacy, airy foliage.

Shape: upright

Shape in flower: same as above

Special Considerations
Special characteristics:
  • aggressive - Self-seeds prolifically.
  • non-invasive
  • native to North America - Mexico
  • butterflies
Special uses:
  • cut flowers
  • direct-seeding
  • wildflowers
Growing Information
How to plant:

Propagate by seed - Scatter seeds outdoors where desired after frost danger has passed, or start indoors 4 to 6 weeks before the last frost. The plants self seed prolifically.

Germination temperature: 70 F to 75 F

Days to emergence: 7 to 14

Maintenance and care:
May require staking. May be weedy due to self seeding. Deadhead to prolong flowering.

More growing information: How to Grow Annuals

Look for dwarfs, various flower colors and plant heights.

‘Cosmic’ Series: Short (1’ tall) plants with colorful yellow or orange flowers. Very reliable bloomer.

‘Sonata’ Series: large flowers in shades of pink, white and red on short, 1 to 2’ tall dwarf plants. Does very well in full sun, and flowers abundantly.

‘Candy Stripe Mix’: white flowers striped along the length of the petals with shades of red.

‘Daydream’: pale pink petals deepend to dark pink towards the tufted yellow center of the flower. Very striking.

‘Gazebo Mix’: white pink and red flowers are larger than most Cosmos and showy on 3 to 4’ tall plants.

‘Seashells Mix’: trumpet-like flower petals are rolled into tubes. Flowers in shades of pink, red and white. Plants grow 3' tall.

‘Sensation’ Series: very large (4 to 6') flowers in a variety of shades of pink, white and red. Plants grow to 4’ tall.

‘Versailles’ Series: excellent for cut flowers because of its wiry stems and large, colorful blooms in shades of red, white and pink. Blooms during short days, and thus is a good winter greenhouse cutflower plant.

‘Picotee' attractive white flowers have reddish pink edges with faint red lines running the length of the petals and yellow flower centers.