Rhododendron x molle ‘Koster’s Brilliant Red’

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Key characteristics

Family: Ericaceae
Height: 3 to 5 ft
Width: 3 to 5 ft
Flower color: Reddish-orange clusters, often with red spotting on the upper petals
Foliage color: Deciduous medium green leaves with orange-red to bronze-red fall color
Bloom time: Late spring to early summer
Light: Full sun to part shade
Water: Moderate
Maintenance: Low; prune lightly only if shaping is needed
Growing zone: USDA zones 5 to 8
Wildlife: Flowers attract pollinators

Shrubs

Rhododendron x molle ‘Koster’s Brilliant Red’

Koster's Brilliant Red Azalea

Rhododendron x molle 'Koster's Brilliant Red' is a deciduous azalea that blooms in late spring, often May into June, with clustered trumpet-shaped flowers in reddish-orange to scarlet tones. The upper petals commonly show small red spots, and the blossoms open as the fresh green leaves expand. Flowers are sometimes lightly fragrant on warm, still spring days, followed by orange-red autumn color.

Raised in Holland by Koster & Sons and introduced in 1918, the name originally covered uniform seedlings repeatedly produced from the same cross, so plants sold under it can show slight variation. It remains valued for its late-spring trusses and warm flower color in woodland borders and mixed shrub plantings.

Light

Full sun to part shade

Water

Moderate

Bloom time

Late spring to early summer

Find this plant

Works well in

Sun Gardens
Borders
Cottage Gardens
Containers

Companion plants

Poppies · Milkweed · Bee balm · Feather reed grass · Rock cress · Alpine mint bush

Design tip

Thread ‘Koster’s Brilliant Red’ through a mixed shrub planting rather than isolating it as a single specimen, allowing its fiery spring color to appear in several places. The repetition draws the eye through the garden and strengthens its later autumn display.

Printable plant sheet (PDF)