Rhododendron 'Irene Koster' (O) | rhododendron 'Irene Koster'

Shrubs

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'Irene Koster' is an decidous azalea, to 2m tall, with fragrant, funnel-shaped rose-pink flowers, blotched yellow, 5cm in width and borne in late spring and early summer

Position

Full sun, Partial shade

Soil Types

Clay, Loam, Sand

Max Height

1-1.5 metres

Max Spread

1-1.5 metres

Size

Time to Maturity: 10–20 years
Max Spread: 1-1.5 metres
Max Height: 1-1.5 metres

Growing Conditions

Clay Loam Sand

Moisture: Moist but well–drained
pH: Acid

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): H5

Colour & Scent

Fragrance Flower

Season	Stem	Flower	Foliage	Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family: Ericaceae
Native to GB/Ireland: 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: Accepted
Horticultural Group

Horticultural Classification Codes

Horticultural Classification Codes are often given to genera which have a large number of species or cultivars. They are used to categorise cultivated plants based on specific, shared characteristics such as shape, colour, size or flowering time, and can be displayed as letters or numbers

For example:
Dahlia ‘Sunset Kate (Sin) = Single flower
Rosa ‘Marigold’ (HT) = Hybrid Tea: Occidentale hybrid azaleas are bushy deciduous shrubs with usually fragrant, funnel-shaped flowers in late spring or early summer

How to Grow

Cultivation

Suitable for an open site but best grown in moist but well-drained, leafy, humus-rich acid soil in part shade with shelter; see rhododendron cultivation

Propagation

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

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Hedging and screens

Pruning

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