Magnolia sieboldii 'Colossus'

RHS Plant Profile

magnolia 'Colossus'

Shrubs Trees

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A large, deciduous shrub or spreading, small tree to 8m tall, the dark green 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. Ornamental fruits turn pink in autumn

Position

Full sun, Partial shade

Soil Types

Clay, Loam, Sand

Max Height

4-8 metres

Max Spread

wider than 8 metres

Size

Time to Maturity: 20–50 years
Max Spread: wider than 8 metres
Max Height: 4-8 metres

Growing Conditions

Clay Loam Sand

Moisture: Moist but well–drained
pH: Acid or Alkaline or Neutral

Position

Full sun Partial shade

Aspect: South–facing or West–facing or East–facing
Exposure: Sheltered
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 & Scent

Fragrance Flower

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Magnoliaceae
Native to GB/Ireland: No
Foliage: Deciduous
Habit: Bushy
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
Name Status: Accepted

How to Grow

Cultivation

Grow in moist but well drained neutral to acid soil in full sun or light shade with shelter from cold winds. Will grow in moist alkaline soils. Late frost may damage the flower buds. For more information see 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

City and courtyard gardens
Architectural
Cottage and informal garden
Low Maintenance
Wall side borders

Pruning

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

Pests

May be susceptible to scale insects, horse chestnut scale and capsid bug

Diseases

May be susceptible to coral spot, phytophthora, grey moulds, honey fungus, a virus or fungal leaf spot