Rhododendron viscosum (Swamp Azalea)

A genuinely wetland-adapted azalea tolerant of periodic flooding, swamp azalea's intensely fragrant flowers draw hummingbirds, bees, and butterflies all summer - though it's worth knowing this species should be kept well away from black walnut and butternut trees, unlike many of its shrub-layer neighbors.

Species Overview

Rhododendron viscosum, commonly called swamp azalea or clammy azalea, is a deciduous shrub native to wetlands, swamps, and bogs across the eastern United States from Maine to Florida and Texas. It grows 3 to 8 feet tall, producing very fragrant, sticky white flowers with a spicy, clove-like scent from May through July - one of the last azaleas to bloom each season.

Application

• Wetland, bog, and stream-margin restoration - flood tolerant
• Rain garden and wet, acidic soil plantings
• Specialist bee habitat (Andrena cornelli) alongside hummingbirds and butterflies
• Fragrant naturalized landscape plantings

Growing Conditions / Specification Data

• Light: Part Shade - tolerates some sun, avoid afternoon exposure
• Soil/Moisture Tolerance: Wet, acidic soils; tolerates seasonal to regular inundation but needs enough drainage to avoid standing water at the roots
• Plant Type: Shrub
• Mature Height: 4-8 ft.
• Fall Color: Red
• Bloom Color / Period: White, Pink; May-August
• Wetland Indicator Status: NI (No Indicator) - see flags
• Native Range: Northeast/Mid-Atlantic (full list)
• Hydrology: Moist-Wet
• Root Depth: Moderate (12-24 in.)
• Salinity Tolerance: Low
• Growth Rate: Moderate
• Drought Tolerance: Low
• Deer Resistance: Some
• Flood Tolerance: High - Commonly called swamp azalea for its association with wet, boggy sites and streamsides; tolerates periodically saturated to standing water.
• Shade Tolerance: Intermediate
• Growth Habit: Multi-stemmed/Thicket-forming
• USDA Hardiness Zones: 4-8
• Juglone Tolerance: Intolerant
• Pollinator Value: Supports bees, supports specialist/oligolectic bees, supports butterflies, supports hummingbirds

Planting Guidance

• IMPORTANT: avoid planting near black walnut and butternut trees - unlike most other shrubs in this catalog, this species is documented as juglone-sensitive rather than tolerant. All plant parts are toxic if ingested.