• 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 viscosum (A)

swamp azalea

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
swamp azalea

© RHS

  • Other common names swamp azalea
    swamp honeysuckle

    white swamp honeysuckle

    see more
  • 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

  • Horticultural Group Azaleas can be deciduous or evergreen, with mostly small, frequently fragrant, funnel-shaped flowers in spring or early summer; deciduous azaleas often have good autumn colour

  • Details R. viscosum is a bushy medium-sized shrub with dark leaves glaucous beneath. Very fragrant, narrowly funnel-shaped white flowers up to 4cm wide, flushed deep pink on the tube, open in early summer

  • Plant range Eastern N America

Characteristics

  • Foliage Deciduous

  • 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)

    H6

Colour

Sunlight

  • Full Sun

  • Partial Shade

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

  • Exposure Sheltered

Soil

  • Loam

    Loam

  • Sand

    Sand

  • MoistureMoist but well-drained

  • SoilLoam, Sand

  • pHAcid

Size

  • Ultimate height 1.5-2.5 metres

  • Ultimate spread 1.5-2.5 metres

  • Time to ultimate height 10-20 years

How to grow

Cultivation Easy to grow in moist, humus-rich acid soil but will not tolerate deep planting. Tolerates partial shade but prefers full sun

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

Suggested planting locations and garden types Flower borders and beds City & Courtyard Gardens Cottage & Informal Garden

How to care

Pruning Pruning group 8

Pests Can get aphids, caterpillars and vine weevil

Diseases May be affected by powdery mildews, a leaf spot and lime induced chlorosis amongst others

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