• 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

Rhododendron grande

© RHS

  • Synonyms Rhododendron argenteum

  • Family Ericaceae

  • 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

  • Details R. grande is a small evergreen tree or large shrub, to 9m tall, with large, leathery leaves, up to 30cm long, dark green above and silvery-white, or covered in a dull, light brown down, beneath. Dense rounded trusses of bell-shaped, cream to pale yellow flowers, each with a purple basal blotch, open from pink buds, in late winter to mid spring

Characteristics

  • Foliage Evergreen

  • Habit Bushy

  • 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)

    H4

Colour

Sunlight

  • Full Sun

  • Partial Shade

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

  • Exposure Sheltered

Soil

  • Loam

    Loam

  • Sand

    Sand

  • MoistureMoist but well-drained

  • SoilLoam, Sand

  • pHAcid

Size

  • Ultimate height 8-12 metres

  • Ultimate spread 2.5-4 metres

  • Time to ultimate height 20-50 years

How to grow

Cultivation Grow in moist but well-drained, leafy, humus-rich acid soil in part shade with shelter; best suited to woodland gardens in milder counties; see rhododendron cultivation

Propagation Propagate by seed when ripe, or semi-ripe cuttings in late summer, layering in autumn or grafting in late summer or late winter

Suggested planting locations and garden types Low Maintenance Architectural Cottage & Informal Garden

How to care

Pruning Pruning group 8

Pests May be attacked by vine weevil, rhododendron leafhopper, pieris lacebug, scale insects, caterpillars and aphids

Diseases May be affected by various Rhododendron diseases including powdery mildews, rhododendron petal blight, rhododendron bud blast, silver leaf and honey fungus

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