Rhododendron arboreum

RHS Plant Profile

tree-like rhododendron

Trees

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A large, narrow, evergreen tree, with dark green leaves, to 20cm long, a smooth cinnamon-brown, fawn or silvery indumentum on the undersides. Flowers, produced in rounded trusses in early spring, are up to 5cm long and may be red, white or any shade of pink, usually with spotting in the throat

Position

Partial shade

Soil Types

Loam, Sand

Max Height

8-12 metres

Max Spread

2.5-4 metres

Size

Time to Maturity: 20–50 years
Max Spread: 2.5-4 metres
Max Height: 8-12 metres

Growing Conditions

Loam Sand

Moisture: Moist but well–drained
pH: Acid

Position

Partial shade

Aspect: South–facing or North–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): H4

Colour & Scent

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Ericaceae
Native to GB/Ireland: No
Foliage: Evergreen
Habit: Columnar upright
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
Plant Range: India & Sino-Himalaya

How to Grow

Cultivation

Grow in moist but well-drained, leafy, humus-rich acid soil in part shade with shelter; see rhododendron cultivation

Propagation

Propagate by seed when ripe, or semi-ripe cuttings in late summer, layering in autumn or grafting in late summer or late winter

Suggested planting locations and garden types

Architectural
Cottage and informal garden
Low Maintenance

Pruning

Pruning group 8

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 various Rhododendron diseases including powdery mildews, rhododendron petal blight, rhododendron bud blast, silver leaf and honey fungus