• 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 'Hummingbird'

common white alder 'Hummingbird'

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
common white alder 'Hummingbird'

© RHS

  • Other common names common white alder 'Hummingbird'

  • 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 'Hummingbird' is a compact shrub, up to 1.2m high, with glossy dark green leaves which turn yellow in autumn. Many feathery spikes of sweetly clove-scented white flowers appear in mid- to late summer

Characteristics

  • Foliage Deciduous

  • Habit Suckering

  • 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)

    H5

Colour

Sunlight

  • Partial Shade

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

  • Exposure Sheltered

Soil

  • Sand

    Sand

  • Loam

    Loam

  • MoistureMoist but well-drained

  • SoilSand, Loam

  • pHAcid

Size

  • Ultimate height 1-1.5 metres

  • Ultimate spread 1-1.5 metres

  • Time to ultimate height 5-10 years

How to grow

Cultivation Grow in humus-rich, moist, well-drained, lime-free soil in dappled shade, in the shelter of an open woodland garden or a lightly-shaded shrub border; after pruning, mulch with well-rotted leaf mould

Propagation Propagate by division of suckers, by heeled semi-ripe cuttings of lateral shoots in summer, or by layering in late autumn or early spring

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

How to care

Pruning Pruning group 1; in winter, remove some of the older stems, leaving the strongest suckers; cut off old flowerheads in spring

Pests Generally pest free

Diseases Generally disease free

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