Cosmos bipinnatus Sea Shells ('Sea Shells') (mixed)

RHS Plant Profile
cosmea [Sea Shells Mixed]

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cosmea [Sea Shells Mixed] RHS
cosmea [Sea Shells Mixed] RHS
cosmea [Sea Shells Mixed] RHS

Other common names

cosmea 'Sea Shells'

Synonyms

Cosmos bipinnatus 'Sea Shells'
Cosmos 'Sea Shells'

Plants for pollinators
Annual Biennial
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A half-hardy annual, to 1m tall, with finely-divided, feathery foliage and blooms with fluted petals in a range of colours from white to pink to carmine red surrounding the central yellow eye

Position

Full sun

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
1 year
Max Spread
0.5-1 metres
Max Height
0.5-1 metres

Growing Conditions

Chalk Clay Loam Sand
Moisture
Moist but well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun
Aspect
West–facing or South–facing or East–facing
Exposure
Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H3

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Genus
Cosmos can be annuals or perennials with simple or pinnately divided leaves and large, long-stalked daisy-like flowers in summer
Name Status
Trade

How to Grow

Cultivation

Grow in moist, but well-drained soil in full sun. Suited to annual or cut-flower borders or as a summer infill

Propagation

See sowing seeds indoors

Suggested planting locations and garden types

  • Patio and container plants
  • Cottage and informal garden
  • Wildlife gardens
  • Flower borders and beds
  • Cut flowers

Pruning

Deadhead to prolong the flowering season

Pests

May be susceptible to aphids and slugs

Diseases

May be susceptible to grey moulds