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Annual Biennial

Cosmos bipinnatus

cosmea

C. bipinnatus is a tall, bushy annual to 2.5m, with very finely divided, mid-green leaves, and large flowers to 8cm across, usually white or pink the wide outer rays surround a central disc of tightly clustered, usually yellow, inner disc florets. Flowering late summer and into autumn, until frost occurs. Many named cultivars and selections are available, including doubles, forms with tubular rays, and picotee colours

Other common names
Mexican aster
purple Mexican aster
see moreSpanish needles
Synonyms
Bidens formosa

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Size
Ultimate height
1.5–2.5 metres
Time to ultimate height
1–2 years
Ultimate spread
0.1–0.5 metres
Growing conditions
Chalk
Loam
Sand
Moisture
Moist but well–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring
Summer Pink White Green
Autumn Pink White Green
Winter
Position
  • Full sun
Aspect

West–facing or South–facing

Exposure
Exposed or Sheltered
Hardiness
H3
Botanical details
Family
Asteraceae
Native to the UK
No
Foliage
Deciduous
Habit
Columnar upright
Genus

Cosmos can be annuals or perennials with simple or pinnately divided leaves and large, long-stalked daisy-like flowers in summer

Name status

Correct

Plant range
Mexico, S US

How to grow

Cultivation

Grow in moderately fertile, moist, but well-drained soil in full sun. Deadhead flowers to prologue flowering season. Leave a few seedheads to ripen to selfseed if required

Propagation

Propagate by seed at 16°C in mid-spring under glass, or in situ in late spring

Suggested planting locations and garden types
  • Cottage and informal garden
  • Wildflower meadow
  • City and courtyard gardens
  • Patio and container plants
  • Prairie planting
  • Wildlife gardens
Pruning

none required

Pests

Aphids and slugs may be troublesome

Diseases

Susceptible to grey moulds

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