• 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

Hydrangea serrata 'Diadem' (L)

Hydrangea 'Diadem'

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
Hydrangea 'Diadem'

© � RHS

  • Other common names Hydrangea 'Diadem'

  • Genus Hydrangea can be deciduous or evergreen shrubs, or self-clinging climbers, with flowers in clusters usually comprising both small fertile and more showy sterile flowers; often good autumn colour

  • Family Hydrangeaceae / Hydrangeaceae

  • Species 'Diadem' is a compact, spreading deciduous shrub with lace-cap flower-heads of pale pink or light blue flowers in early summer

  • Horticultural Group Lace cap hydrangeas are compact deciduous shrubs with broadly ovate leaves and flat or gently domed clusters of small fertile flowers, with showy sterile flowers around the margin

Characteristics

  • Foliage Deciduous

  • Habit Bushy

  • Toxicity May cause mild stomach upset if ingested

  • 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

    H5

Colour

Sunlight

  • Full Sun

  • Partial Shade

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

  • Exposure Sheltered or Exposed

Soil

  • Chalk

    Loam

  • Chalk

    Clay

  • Chalk

    Sand

  • MoistureWell-drained, Moist but well-drained

  • SoilLoam, Clay, Sand

  • pHAcid, Neutral

Size

  • Ultimate height

    0.5-1 metres

  • Ultimate spread

    0.5-1 metres

  • Time to ultimate height

    5-10 years

How to grow

Cultivation Grow in moist but well-drained soil in sun or partial shade

Propagation Propagate by softwood cuttings

Suggested planting locations and garden types Flower borders and beds Wall-side Borders City & Courtyard Gardens Coastal Cottage & Informal Garden

How to care

Pruning Pruning group 1

Pests Can get aphids, capsid bug, glasshouse red spider mite and hydrangea scale

Diseases Generally disease free

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