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Shrubs

Rhododendron molle subsp. japonicum (M)

Japanese azalea

A deciduous azalea up to 2m high, with an upright habit, and green leaves that are softly hairy underneath. Young shoots and flower buds also have a covering of fine downy hairs. Flowers are produced before the leaves in spring, and are scented, broadly funnel-shaped, and usually shades of orange or coral red. Leaves are often richly coloured in autumn

Synonyms

Rhododendron molle Siebold & Zucc.
Rhododendron japonicum (A. Gray) Valck.Sur.

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Ultimate height

1.5–2.5 metres

Time to ultimate height

5–10 years

Ultimate spread

1.5–2.5 metres

Clay

Loam

Sand

Moisture

Moist but well–drained

pH

Acid

	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Full sun
Partial shade

Aspect

South–facing or West–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)

Botanical details

Family: Ericaceae
Native to the UK: No
Foliage: Deciduous
Habit: Bushy
Potentially harmful: Harmful if eaten. Wear gloves and other protective equipment when handling. Pets (dogs, cats, rabbits, tortoises) Harmful if eaten - for further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
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
Name status: Correct
Horticultural Group: Mollis azaleas are deciduous shrubs with unscented, funnel-shaped flowers in a range of colours from white through yellow and orange, to red, opening before the leaves in late spring
Plant range: Japan

How to grow

Cultivation

Grow in moist but well-drained, humus rich, acidic soil, in sun or light shade. Choose a site away from frost pockets and sheltered from strong winds. Mulch annually, ideally with leaf mould. See rhododendron cultivation for more detailed advice

Propagation

Propagate by seed or by semi-ripe cuttings in late summer

Suggested planting locations and garden types

Cottage and informal garden
Low Maintenance
Flower borders and beds

Pruning

Prune lightly after flowering, see pruning group 1

Pests

May be susceptible to vine weevil, rhododendron and azalea whitefly, rhododendron leafhopper, Pieris lacebug, scale insects, caterpillars and aphids

Diseases

May be susceptible to powdery mildews, honey fungus, silver leaf and Phytophthora, as well as more specific Rhododendron diseases

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