• 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

Rhododendron decorum

Great white rhododendron

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
Great white rhododendron

© � RHS

  • Other common names Great white rhododendron

  • Genus Rhododendron can be evergreen or deciduous shrubs or trees, with simple leaves, sometimes with a dense colourful indumentum of hairs on the lower side, and funnel-shaped, bell-shaped or tubular flowers that may be solitary or in short racemes

  • Family Ericaceae / Ericaceae

  • Species R. decorum is a large evergreen shrub or small tree, with oblong leaves, pale beneath, and trusses of large, strongly fragrant, funnel-shaped white or pink-tinged flowers, greenish-yellow in the throat

  • Plant range China Myanmar Laos

Characteristics

  • Foliage Evergreen

  • Habit Bushy

  • 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)
    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

    H4

Colour

Sunlight

  • Full Sun

  • Partial Shade

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

  • Exposure Sheltered

Soil

  • Chalk

    Sand

  • Chalk

    Clay

  • Chalk

    Loam

  • MoistureMoist but well-drained

  • SoilSand, Clay, Loam

  • pHAcid

Size

  • Ultimate height

    4-8 metres

  • Ultimate spread

    1.5-2.5 metres

  • Time to ultimate height

    10-20 years

How to grow

Cultivation Grow in moist but well-drained, leafy humus-rich, acid soil. Shallow planting is essential, deep planting will not be tolerated

Propagation Propagate by seed or semi-hardwood cuttings. Cultivars will not come true from seed

Suggested planting locations and garden types Banks and Slopes Flower borders and beds Hedging & Screens Low Maintenance Wall-side Borders Cottage & Informal Garden Patio & Container Plants

How to care

Pruning Pruning group 8

Pests May be attacked by vine weevil, leafhoppers, lacebugs, scale insects, caterpillars and aphids

Diseases May be subject to powdery mildews, rhododendron petal blight, rhododendron bud blast and silver leaf

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