• AGM plants

    AGM plants have been through a rigourous 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

Sidalcea 'William Smith'

Prairie mallow 'William Smith'

AGM plants

AGM plants have been through a rigourous 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
Prairie mallow 'William Smith'

© � RHS 2002

  • Other common names Prairie mallow 'William Smith'

  • Genus Sidalcea can be annuals or perennials, forming a clump of rounded or palmately lobed basal leaves, with erect stems bearing more deeply divided leaves and terminal racemes of 5-petalled mallow-like flowers

  • Family Malvaceae / Malvaceae

  • Species 'William Smith' is an erect herbaceous perennial making a clump to 90cm in height, with rounded basal leaves and deeply lobed stem leaves. Flowers 5cm in width, with five salmon tinted, deep rose-pink petals

Characteristics

  • Foliage Deciduous

  • Habit Clump-forming

  • 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)
    Old hardiness ratings

    While we update our systems with the new hardiness ratings you may still see old hardiness ratings in your search results. These are denoted as 'Old'.

    • H1 - Requires heated glass
    • H2 - Requires unheated glass
    • H3 - Hardy outside in some regions of the UK
    • H4 - Hardy throughout the UK
    • H1 + H3 - Requires heated glass but may be grown outside in summer

    For full details of the hardiness ratings see

    see more

    H7

Colour

Sunlight

  • Full Sun

  • Aspect South-facing

  • Exposure Exposed or Sheltered

Soil

  • Chalk

    Sand

  • Chalk

    Loam

  • MoistureMoist but well-drained

  • SoilSand, Loam

  • pHAcid, 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 Best grown in moderately fertile, humus-rich, moist but well-drained, light, sandy, neutral to slightly acid soil in full sun; will tolerate other soils but resents waterlogging. Provide a dry mulch of bracken or straw during cold winters

Propagation Propagate by division in autumn or spring

Suggested planting locations and garden types Flower borders and beds Cut Flowers Cottage & Informal Garden Prairie Planting

How to care

Pruning Cut stems back hard after flowering to encourage further flowers and to prevent self-seeding

Pests Slugs may be a problem

Diseases May be subject to a rust

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