Growing Guide
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Cosmos (C. sulphureus)

Annual Flower

Also known as Mexican Aster
Cosmos sulphureus
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 warm colors 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
  • orange
  • yellow

Foliage color: medium green

Foliage texture: fine

Very lacy, airy foliage. 'Ladybird' Series has less feathery leaves.

Shape: upright

Shape in flower: same as above

Special Considerations
Special characteristics:
  • aggressive - Self-seeds prolifically.
  • non-invasive
  • native to North America - North and South America
  • 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.

‘Ladybird’ Series: yellow, orange or red semi-double flowers on dwarf 1 to 1 ˝’ tall plants. Leaves are not feathery like other Cosmos.

‘Polidor’ mix: 2” flowers in shades of yellow and orange on 2 to 2 ˝’ tall plants.