• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Silphium perfoliatum

cup plant

AGM plants

AGM plants have been through a rigorous trial and assessment programme. They are:

  • Excellent for ordinary use in appropriate conditions
  • Available to buy
  • Of good constitution
  • Essentially stable in form & colour
  • Reasonably resistant to pests & diseases
cup plant

© RHS

  • Other common names cup plant
    cup rosin weed

    Indian cup

    see more
  • Family Asteraceae

  • Genus Silphium are robust herbaceous perennials with tall stems bearing simple leaves, aromatic when bruised, and loose clusters of yellow, daisy-like flowers in summer and early autumn

  • Details S. perfoliatum is an upright perennial to 2.5m tall, with paired, oval leaves joined around the stem, and branched sprays of bright yellow daisies 7-9cm wide, opening in late summer

  • Plant range E N America

Characteristics

  • Foliage Deciduous

  • Habit Bushy

  • Fragrance Leaf

  • 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)

    H7

Colour

Sunlight

  • Full Sun

  • Partial Shade

  • Aspect South-facing or West-facing

  • Exposure Exposed or Sheltered

Soil

  • Chalk

    Loam

  • MoistureWell-drained, Moist but well-drained

  • SoilLoam

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height 1.5-2.5 metres

  • Ultimate spread 0.5-1 metres

  • Time to ultimate height 2-5 years

How to grow

Cultivation An impressive plant suitable for the back of a border. It performs best when grown in full sun; in partial shady, or windy, sites it may require staking

Propagation Propagate by seed or division

Suggested planting locations and garden types Flower borders and beds Architectural Cottage & Informal Garden

How to care

Pruning Cut back after flowering; stems may optionally be left until shortly before new growth begins the following season

Pests Generally trouble free

Diseases Generally trouble free

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