Rhododendron schlippenbachii, royal azalea
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Deciduous Shrubs

Rhododendron schlippenbachii

royal azalea

Ericaceae

Korea, northeastern China, Russian Far East

At a Glance

TypeShrub
HabitMounding
FoliageDeciduous
Height4-8 feet (1.2-2.4 m)
Width4-8 feet (1.2-2.4 m)
Maturity12 years

Growing Zones

USDA Hardiness Zones

4 - 8
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Attracts Pollinators
Attracts Butterflies
Deer Resistant
Fragrant (light)
Container Friendly
Maintenancelow

Overview

Rhododendron schlippenbachii is a deciduous azalea reaching 4-8 feet (1.2-2.4 m) tall in cultivation (to 15 feet / 4.6 m in native habitat) with a spread of 4-8 feet (1.2-2.4 m), developing a rounded, well-branched form with an elegant, open architecture. Widely regarded as one of the finest deciduous azaleas, this species was named for Baron Alexander von Schlippenbach, a Russian naval officer who collected it in Korea in 1854. Bark is smooth, light gray-brown. Leaves are distinctive: obovate to broadly rounded, 2-4.5 inches (5-11 cm) long, arranged in whorls of 5 at the branch tips, giving a uniquely architectural quality. Foliage emerges with the flowers in April to May, medium green in summer, turning yellow, orange, burgundy, and crimson in fall — among the most spectacular fall color displays of any rhododendron. Flowers are saucer-shaped to broadly funnel-shaped, 2.5-3.5 inches (6-9 cm) across, pale pink to rose-pink with reddish-brown spotting on the upper petal, borne in trusses of 3-6 at branch tips concurrent with leaf emergence. Flowers are lightly fragrant. Growth rate is slow at 2-4 inches (5-10 cm) per year. Cold-hardy to -20°F (-29°C). Sensitive to late spring frosts, which can damage flowers and emerging foliage. All parts are toxic if ingested.

Native Range

Native to Korea, northeastern China (Manchuria), and the Russian Far East (Primorsky Krai). Occurs in open deciduous forests and forest margins at elevations of 1,000-5,000 feet (300-1,500 m). The national flower of North Korea.

Suggested Uses

Planted as a specimen or in woodland gardens and shade borders where its distinctive whorled foliage, spring flowers, and fall color can be appreciated at close range, spaced 4-6 feet (1.2-1.8 m) apart. Combines well with other acid-loving woodland plants. The slow growth and refined form make it suitable for smaller gardens. Fall foliage color is equal to or surpasses the spring flower display in ornamental value. A Great Plant Picks recommendation for the Pacific Northwest.

How to Identify

Identified by distinctive whorls of 5 obovate to broadly rounded leaves at each branch tip, saucer-shaped pale pink to rose-pink flowers with reddish-brown spotting, and rounded growth habit. Distinguished from other deciduous azaleas by the uniquely whorled leaf arrangement (most azaleas have alternate or clustered, non-whorled leaves). Distinguished from Rhododendron quinquefolium (which also has whorled leaves) by pink (not white) flowers and larger leaves.

Appearance

Size & Dimensions

Height4' - 8'
Width/Spread4' - 8'

Reaches mature size in approximately 12 years

Colors

Flower Colors

pink

Foliage Colors

green

Fall Foliage Colors

yellow
orange
red

Bloom Information

Bloom Period

~3 weeks
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Spring
Flowers appear in April to May concurrent with leaf emergence, in trusses of 3-6. In the Pacific Northwest, bloom typically occurs in mid- to late April, lasting 2-3 weeks. Flowers are lightly fragrant. Late spring frosts can damage both open flowers and emerging foliage. Site in a sheltered location to reduce frost risk.

Detailed Descriptions

Flower Description

Pale pink to rose-pink with reddish-brown spotting

Foliage Description

Medium green, whorled

Growing Conditions

Sun Requirements

Partial Shade
Requires 3-6 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

Soil Requirements

pH Range4.5 - 6.0(Acidic)
357912
Soil Types
loampeat
Drainage
well drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

5-7 years

Care & Maintenance

Care Guide

Water regularly; the shallow, fibrous root system requires consistent moisture. Maintain 2-4 inches (5-10 cm) of organic mulch. Plant in part shade with 3-6 hours of direct light; morning sun with afternoon shade is ideal. Requires acidic, well-drained, humus-rich soil (pH 4.5-6.0). Avoid disturbance of the shallow root system. Slow growth rate requires patience; do not attempt to accelerate growth with heavy fertilization. Apply a light application of acidic fertilizer in early spring. Protect from late spring frosts, which damage both flowers and emerging foliage; site in a sheltered location away from frost pockets. Protect from drying winter winds.

Pruning

Prune immediately after flowering in May to June. Remove spent flower trusses. The naturally well-branched, rounded form requires minimal shaping. Remove dead, damaged, and crossing branches. Selective removal of oldest stems at ground level every 5-7 years promotes gradual rejuvenation. Avoid heavy pruning; slow growth rate means recovery is very slow.

Pruning Schedule

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late spring

Maintenance Level

low

Container Growing

✓ Suitable for container growing

Minimum container size: 7 gallons

⚠️ Toxicity Warning

Toxic to pets and humans
Rhododendron schlippenbachii (royal azalea) - Identification & Care Guide | PlantRef