Rhododendron occidentale, western azalea
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Deciduous Shrubs

Rhododendron occidentale

western azalea

Ericaceae

Western North America (Oregon, California)

At a Glance

TypeShrub
HabitUpright
FoliageDeciduous
Height4-10 feet (1.2-3 m)
Width4-8 feet (1.2-2.4 m)
Maturity10 years

Growing Zones

USDA Hardiness Zones

6 - 9
Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Attracts Pollinators
Attracts Butterflies
Deer Resistant
Fragrant (strong)
Container Friendly
Native to North America
Maintenancemoderate

Overview

Rhododendron occidentale is a deciduous azalea reaching 4-10 feet (1.2-3 m) tall with a spread of 4-8 feet (1.2-2.4 m), developing an upright to spreading, multi-stemmed form. This is the only azalea native to the western United States and one of the most fragrant of all rhododendrons. Bark is smooth, gray-brown on older stems. Leaves are alternate, simple, obovate to oblanceolate, 1.5-3.5 inches (4-9 cm) long, clustered near branch tips, medium to bright green, turning yellow, orange, scarlet, and crimson in fall — among the most vivid fall color displays of any Pacific Northwest native shrub. Funnel-shaped flowers, 1.5-2.5 inches (4-6 cm) across, are borne in trusses of 6-12 at branch tips in May to July, after leaf emergence. Flower color is predominantly white to pale pink with a prominent yellow-orange blotch on the upper petal; color variants range from cream to deep pink and rose, occasionally with salmon tones. Fragrance is intense, sweet, and honeysuckle-like, detectable from considerable distance. Growth rate is slow to moderate at 3-6 inches (8-15 cm) per year. Found naturally along streams, seeps, and moist openings in forests, often in serpentine or other nutrient-poor soils. All parts are toxic if ingested, containing grayanotoxins. Wild populations have declined due to habitat loss, and several regional populations are of conservation concern.

Native Range

Native to western North America from southwestern Oregon south through the Coast Ranges, Klamath Mountains, Sierra Nevada, and San Bernardino Mountains of California. Occurs along streams, seeps, bogs, and moist meadow margins from sea level to 7,500 feet (2,300 m), typically on acidic, nutrient-poor soils. One parent species of many Occidentale hybrid azaleas.

Suggested Uses

Planted in woodland gardens, stream-side plantings, and native plant gardens where acidic, moist soil conditions can be maintained, spaced 3-5 feet (0.9-1.5 m) apart. Combines well with native ferns, Cornus nuttallii, and other acid-loving woodland plants. Fall foliage color and intense flower fragrance are primary ornamental features. Conservation plantings support declining native populations. Suitable for containers with acidic potting mix (minimum 7-gallon pot).

How to Identify

Identified by its deciduous habit, funnel-shaped white to pink flowers with a yellow-orange blotch on the upper petal, intense sweet fragrance, and obovate leaves clustered near branch tips. Distinguished from Rhododendron japonicum by white (not orange-red) flowers, more prominent yellow blotch, and stronger fragrance. Distinguished from Exbury/Knap Hill hybrids by typically white-to-pink color range and later bloom period.

Appearance

Size & Dimensions

Height4' - 10'
Width/Spread4' - 8'

Reaches mature size in approximately 10 years

Colors

Flower Colors

white
pink

Foliage Colors

green

Fall Foliage Colors

yellow
orange
scarlet
red

Bloom Information

Bloom Period

~3 weeks
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SpringSummer
Funnel-shaped flowers in trusses of 6-12 appear in May to July, after leaf emergence — later than most other deciduous azaleas. In the Pacific Northwest, bloom typically occurs in late May to June, lasting 2-3 weeks. Fragrance is intense and sweet, carrying over considerable distance. Deadheading spent trusses improves plant vigor.

Detailed Descriptions

Flower Description

White to pale pink with yellow-orange blotch

Foliage Description

Medium to bright green

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
moist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

3-5 years

Care & Maintenance

Care Guide

Water regularly; this species occurs naturally along streams and seeps and requires consistent moisture, particularly during summer. Maintain 2-4 inches (5-10 cm) of organic mulch over the root zone. Plant in part shade with 3-6 hours of direct light; tolerates more sun with adequate moisture. Requires acidic soil (pH 4.5-6.0); performs poorly on alkaline or heavy clay soils. Avoid disturbance of the shallow, fibrous root system. Slow to establish; patience is required during the first 2-3 years. Do not fertilize heavily; the species is adapted to nutrient-poor soils. In the Pacific Northwest, performs best in cooler, moister locations; struggles in hot, dry summer conditions without supplemental irrigation.

Pruning

Prune immediately after flowering in June to July, before next year's flower buds form. Remove spent flower trusses. Shape by cutting back to a lateral branch or dormant bud. Avoid heavy pruning; deciduous azaleas recover slowly. Remove dead, damaged, and crossing branches at any time. Selective removal of oldest stems at ground level every few years promotes rejuvenation.

Pruning Schedule

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Maintenance Level

moderate

Container Growing

✓ Suitable for container growing

Minimum container size: 7 gallons

⚠️ Toxicity Warning

Toxic to pets and humans