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Rhododendron schlippenbachii
royal azalea
Korea, northeastern China (Manchuria), and the Russian Far East; open oak woodlands and mountain slopesLearn more
Overview
Rhododendron schlippenbachii is royal azalea (Schlippenbach azalea), a mounding deciduous shrub growing 4-8 feet (1.2-2.4 m) tall and 4-8 feet (1.2-2.4 m) wide. Pale pink to white broadly funnel-shaped flowers 3 inches (7 cm) with reddish-brown spots on the upper petals, in terminal trusses of 3-6 appearing with or just before the new leaves in April-May. Lightly fragrant. Medium green broadly obovate leaves 2-4 inches (5-10 cm) arranged in distinctive whorls of 5 at branch tips — this whorled arrangement is the key identifying feature. Turns yellow, orange, and red in fall. In Ericaceae. Native to Korea, northeastern China, and the Russian Far East. Named for Baron Alexander von Schlippenbach who collected it in Korea in the 1850s. Requires acidic well-drained soil (pH 4.5-6.0) — iron chlorosis and decline in alkaline conditions. This acid-soil requirement is the primary limitation. Slow-growing — reaches mature size over 8+ years. The shallow fibrous root system does not tolerate compaction or deep mulching. Not drought-tolerant — consistent moisture required. Flower buds formed in the previous summer can be damaged by late frost in zone 4. All parts are toxic (grayanotoxins). Zones 4-8. Part shade. Growth rate is slow.
Native Range
Native to Korea, northeastern China (Manchuria), and the Russian Far East. Found in open oak woodlands and mountain slopes.Suggested Uses
Grown in woodland gardens, shade borders, and in containers of at least 10 gallons (38 L), spaced 4-8 feet (1.2-2.4 m). Whorled leaf arrangement. Fall color. Requires acidic soil. Slow-growing. Toxic. Zones 4-8.How to Identify
Appearance
Size & Dimensions
Height4' - 8'
Width/Spread4' - 8'
Reaches mature size in approximately 8 years
Bloom Information
Mid spring (April-May). Pale pink to white broadly funnel-shaped flowers 3 inches (7 cm) with reddish-brown spots, in trusses of 3-6 appearing with or just before leaves. Lightly fragrant. 2 weeks of bloom. Bee- and butterfly-visited.Detailed Descriptions
Flower Description
Pale pink to white with reddish-brown spots on the upper petals, broadly funnel-shaped, 3 inches (7 cm) across, in terminal trusses of 3-6 appearing with or just before the new leavesFoliage Description
Medium green, broadly obovate, 2-4 inches (5-10 cm), arranged in distinctive whorls of 5 at branch tips; turns yellow, orange, and red in fallGrowing Conditions
Sun Requirements
Requires 4-6 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Part shade (4-6 hours — morning sun with afternoon shade). Acidic well-drained soil pH 4.5-6.0. Not drought-tolerant — consistent moisture required. Shallow fibrous roots — mulch no deeper than 2 inches (5 cm). Slow-growing. Flower buds can be damaged by late frost in zone 4. Deadhead spent trusses. Prune after flowering (May-June). Toxic (grayanotoxins). Zones 4-8.Pruning
Prune lightly after flowering (May-June) — flower buds for next year form in summer. Shape lightly if needed — do not shear. Remove dead or crossing branches. The mounding rounded form is natural. Slow-growing — minimal pruning needed.Pruning Schedule
J
F
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A
M
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late spring
Maintenance Level
lowContainer Growing
✓ Suitable for container growing
Minimum container size: 10 gallons