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Cosmos atrosanguineus

chocolate cosmos

© RHS 2002
Sold by 20 nurseries

  • Other common names chocolate cosmos
    black cosmos

    black dahlia

    see more

  • Synonyms Bidens atrosanguinea
    Cosmos atrosanguineus 'Chocolate'

    Cosmos diversifolius atrosanguineus

    see more

  • Family Asteraceae

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

  • Details C. atrosanguineus is a spreading tuberous perennial, with pinnately divided leaves and bowl-shaped, chocolate-scented, maroon-crimson flower-heads in late summer

  • Plant range Mexico

Characteristics

  • Foliage Deciduous

  • Habit Spreading / Branched

  • Fragrance Flower

  • 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

Sunlight

  • Full Sun

  • Aspect South-facing or East-facing or West-facing

  • Exposure Exposed or Sheltered

Soil

  • Loam

    Loam

  • Chalk

    Chalk

  • Sand

    Sand

  • MoistureMoist but well-drained

  • SoilLoam, Chalk, Sand

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height 0.5-1 metres

  • Ultimate spread 0.1-0.5 metres

  • Time to ultimate height 2-5 years

How to grow

Cultivation Grow in a moderately fertile, moist but well-drained soil in full sun. Mulch in autumn; in cold areas lift tubers before first frosts and keep frost-free over winter.

Propagation Propagate by taking basal cuttings in early spring and providing bottom heat

Suggested planting locations and garden types Flower borders and beds Cut Flowers City & Courtyard Gardens Cottage & Informal Garden

How to care

Pruning Deadhead to prolong flowering

Pests Generally pest free

Diseases May suffer from foot rot and grey moulds

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