• 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

Clethra alnifolia 'Paniculata'

sweet pepper bush

sweet pepper bush

© RHS 2002

  • Other common names sweet pepper bush
    panicled white alder

  • Synonyms Clethra alnifolia var. paniculata
    Clethra paniculata

  • Family Clethraceae

  • Genus Clethra can be deciduous or evergreen trees or shrubs, sometimes with attractive bark, with simple leaves and small, fragrant, usually white, bell-shaped flowers in racemes or panicles

  • Details 'Paniculata' is a bushy deciduous medium-sized shrub with finely-toothed, obovate leaves, and small fragrant white flowers in panicles at the shoot-tips


  • 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)




  • Partial Shade

  • Full Shade

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

  • Exposure Sheltered


  • Chalk


  • Chalk


  • Chalk


  • MoistureMoist but well-drained

  • SoilLoam, Clay, Sand

  • pHAcid


  • 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 Grow in moist, acidic soils in a sheltered position in partial shade or shade

Propagation Propagate by seed or softwood cuttings

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

How to care

Pruning Pruning group 1

Pests Generally pest free

Diseases Generally disease free

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