• 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

Magnolia sieboldii 'Colossus'

magnolia 'Colossus'

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
magnolia 'Colossus'

© Wolfgang Bopp

  • Other common names magnolia 'Colossus'

  • Family Magnoliaceae

  • Genus Magnolia can be deciduous or evergreen trees or shrubs, with large, showy, often fragrant flowers, often opening before the leaves, and sometimes followed by colourful cone-like fruit

  • Details 'Colossus' forms a large, deciduous shrub or spreading, small tree. The leaves are up to 30cm long and 15cm wide, and the flowers, up to 15cm across, appear in late spring and early into midsummer. These are strongly scented, bowl-shaped, with 10-15 white petals and a large boss of deep red stamens in the centre. The ornamental fruits turn pink in autumn

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 East-facing or South-facing or West-facing

  • Exposure Sheltered

Soil

  • Clay

    Clay

  • Loam

    Loam

  • Sand

    Sand

  • MoistureMoist but well-drained

  • SoilClay, Loam, Sand

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height 4-8 metres

  • Ultimate spread wider than 8 metres

  • Time to ultimate height 20-50 years

How to grow

Cultivation Grow in moisture-retentive, well-drained soil in sun or part shade with shelter from cold winds. Further magnolia cultivation advice

Propagation Propagate by softwood cuttings from late spring to early summer, or semi-ripe cuttings from late summer to autumn

Suggested planting locations and garden types Low Maintenance Wall-side Borders Architectural City & Courtyard Gardens Cottage & Informal Garden

How to care

Pruning Magnolia pruning should be carried out in midsummer when in full leaf

Pests Susceptible to scale insects

Diseases Susceptible to coral spot, honey fungus and phytophthera root rot

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