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Clammy Azalea Rhododendron viscosum

Other Common Name(s):

Phonetic Spelling
rho-doh-DEN-dron vis-KOH-sum
This plant has high severity poison characteristics.
See below
Description

The swamp azalea is a woody, broadleaf evergreen or deciduous shrub in the Ericaceae (blueberry) family and is native to the southern and eastern United states. The genus name derives from the Greek words rhodo, which means rose, and dendron, meaning tree.

Its common name rightfully infers a tolerance for damp, moist environments but it requires enough drainage to avoid roots in constant standing water. The swamp azalea likes part shade and can tolerate some sun. Avoid afternoon sun which can scorch the leaves.

This shrub has very fragrant, sticky, white flowers that bloom from May to July and attract hummingbirds, bees, and other pollinators.

It can be planted in naturalized landscapes with careful attention paid to its growing requirements. It grows 2 feet to 8 feet tall and about as wide. It is a spreading shrub.  Use it as a specimen in a native garden or an understory shrub in woodland planting.

Insects, Diseases, and Other Plant Problems: While these shrubs remain very popular for landscape use, many cultivars are susceptible to Phytophthora root rot—this leads to leaf loss, reduced vigor, branch dieback, and wilting. Implement good cultural practices first, such as improving drainage with organic matter or berms and avoiding overwatering or overfertilization. However, if you have a site with a history of this disease, consider planting a root rot-resistant alternative species. 

For suitable alternatives, see this video created by Charlotte Glen as part of the Plants, Pests, and Pathogens series.

 VIDEO Created by Elizabeth Meyer for "Trees, Shrubs and Conifers" a plant identification course offered in partnership with Longwood Gardens.

More information on Rhododendron.

Profile Video:
See this plant in the following landscape:
Cultivars / Varieties:
  • 'Lemon Drop'
  • 'Pink Mist'
  • 'Pink Rocket'
  • 'Viscosum'
'Lemon Drop' , 'Pink Mist', 'Pink Rocket' , 'Viscosum'
Tags:
#hummingbirds#evergreen#deciduous#poisonous#heat tolerant#drought tolerant#wildlife plant#moths#nectar plant#native shrub#rabbit resistant#specialized bees#NC native#pollinator plant#naturalized area#larval host plant#food source summer#food source fall#NC Native Pollinator Plant#Coastal OBL#food source herbage#food source nectar#food source pollen#Piedmont Mountains FACW#wet soils tolerant#mammals#understory shrub#problem for cats#problem for dogs#bee friendly#problem for horses#Audubon#woodland garden
 
Cultivars / Varieties:
  • 'Lemon Drop'
  • 'Pink Mist'
  • 'Pink Rocket'
  • 'Viscosum'
'Lemon Drop' , 'Pink Mist', 'Pink Rocket' , 'Viscosum'
Tags:
#hummingbirds#evergreen#deciduous#poisonous#heat tolerant#drought tolerant#wildlife plant#moths#nectar plant#native shrub#rabbit resistant#specialized bees#NC native#pollinator plant#naturalized area#larval host plant#food source summer#food source fall#NC Native Pollinator Plant#Coastal OBL#food source herbage#food source nectar#food source pollen#Piedmont Mountains FACW#wet soils tolerant#mammals#understory shrub#problem for cats#problem for dogs#bee friendly#problem for horses#Audubon#woodland garden
  • Attributes:
    Genus:
    Rhododendron
    Species:
    viscosum
    Family:
    Ericaceae
    Life Cycle:
    Woody
    Country Or Region Of Origin:
    Southeast and west to Texas
    Wildlife Value:
    Members of the genus Rhododendron support the following specialized bee: Andrena (Andrena) cornelli. Tolerates damage by rabbits.
    Dimensions:
    Height: 2 ft. 0 in. - 8 ft. 0 in.
    Width: 3 ft. 0 in. - 8 ft. 0 in.
  • Whole Plant Traits:
    Plant Type:
    Native Plant
    Poisonous
    Shrub
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Deciduous
    Semi-evergreen
    Habit/Form:
    Open
    Spreading
    Maintenance:
    Low
  • Cultural Conditions:
    Light:
    Full sun (6 or more hours of direct sunlight a day)
    Partial Shade (Direct sunlight only part of the day, 2-6 hours)
    Soil Texture:
    High Organic Matter
    Soil pH:
    Acid (<6.0)
    Soil Drainage:
    Good Drainage
    Moist
    Occasionally Wet
    Available Space To Plant:
    3 feet-6 feet
    NC Region:
    Coastal
    Mountains
    Piedmont
    USDA Plant Hardiness Zone:
    4a, 4b, 5b, 5a, 6b, 6a, 7b, 7a, 8a, 8b, 9b, 9a
  • Fruit:
    Display/Harvest Time:
    Fall
    Summer
    Fruit Type:
    Capsule
    Fruit Description:
    Elongated capsule. Displays from July to October.
  • Flowers:
    Flower Color:
    White
    Flower Inflorescence:
    Raceme
    Flower Value To Gardener:
    Fragrant
    Showy
    Flower Bloom Time:
    Summer
    Flower Shape:
    Tubular
    Flower Petals:
    4-5 petals/rays
    fused petals
    Flower Description:
    Very fragrant, sticky white flowers bloom from May to July in a terminal cluster, tubular, 5-parted.
  • Leaves:
    Woody Plant Leaf Characteristics:
    Broadleaf Evergreen
    Deciduous
    Semi-evergreen
    Leaf Color:
    Green
    Red/Burgundy
    Leaf Type:
    Simple
    Leaf Arrangement:
    Alternate
    Leaf Margin:
    Entire
    Serrate
    Hairs Present:
    No
    Leaf Description:
    Alternate, simple, lustrous green leaves; smooth- or toothed-margined
  • Stem:
    Stem Is Aromatic:
    No
  • Landscape:
    Landscape Location:
    Naturalized Area
    Woodland
    Landscape Theme:
    Butterfly Garden
    Pollinator Garden
    Design Feature:
    Specimen
    Attracts:
    Bees
    Butterflies
    Moths
    Pollinators
    Small Mammals
    Specialized Bees
    Resistance To Challenges:
    Heat
    Rabbits
    Wet Soil
    Problems:
    Poisonous to Humans
    Problem for Cats
    Problem for Dogs
    Problem for Horses
  • Poisonous to Humans:
    Poison Severity:
    High
    Poison Symptoms:
    Salivation, watering of eyes and nose, abdominal pain, loss of energy, depression, nausea and vomiting, diarrhea, weakness, difficult breathing, progressive paralysis of arms and legs, coma.
    Poison Toxic Principle:
    Andromedotoxin
    Causes Contact Dermatitis:
    No
    Poison Part:
    Bark
    Flowers
    Fruits
    Leaves
    Roots
    Seeds
    Stems