• 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

Romneya coulteri

Californian tree poppy

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
  • Other common names Californian tree poppy
    Californian poppy

    bush poppy
    canyon poppy
    dream of the desert
    giant white Californian poppy
    Matilija poppy

    see more
  • Family Papaveraceae

  • Genus Romneya are suckering subshrubs with pinnately lobed leaves and large white flowers in summer

  • Details R. coulteri is a vigorous, suckering herbaceous perennial to 2m in height, with divided, grey-green leaves and poppy-like flowers 15cm in width, with crinkled, pure white petals and a boss of deep yellow stamens

  • Plant range California, Mexico

Characteristics

  • Foliage Deciduous

  • Habit Suckering

  • 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)

    H5

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or West-facing

  • Exposure Sheltered

Soil

  • Loam

    Loam

  • Sand

    Sand

  • MoistureWell-drained, Moist but well-drained

  • SoilLoam, Sand

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height 1.5-2.5 metres

  • Ultimate spread 1-1.5 metres

  • Time to ultimate height 5-10 years

How to grow

Cultivation Grow against a warm, sunny wall protected from cold winds. Mulch deeply prior to winter. They dislike transplanting but once established it can spread, so site with care

Propagation Propagate by basal cuttings in spring, root cuttings in winter or propagate by seed sown in spring at 13°C to 16°C

Suggested planting locations and garden types Drought Resistant Wall-side Borders Mediterranean Climate Plants Cottage & Informal Garden

How to care

Pruning Pruning group 6

Pests Caterpillars may be a problem

Diseases Powdery mildews may be a problem

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