Rhododendron viscosum (L.) Torr.
Swamp Azalea, Clammy Azalea, Cory Azalea, Hammock Sweet Azalea
Ericaceae (Heath Family)
Synonym(s): Azalea serrulata, Azalea viscosa, Rhododendron coryi, Rhododendron serrulatum, Rhododendron viscosum var. aemulans, Rhododendron viscosum var. glaucum, Rhododendron viscosum var. montanum, Rhododendron viscosum var. nitidum, Rhododendron viscosum var. serrulatum, Rhododendron viscosum var. tomentosum
USDA Symbol: rhvi2
Clammy azalea is a loose, open, deciduous shrub growing to 12 ft. in width, but averaging only about 5 ft. tall. The leaves, clustered at the end of branches, are 1 1/2-3 1/2 inches long and 5/8-1 1/2 inches wide, deciduous, lustrous, green on both sides, with short stems. The sweet-scented flowers are white, with a lavender tube slightly enlarged at the base, 1 1/4-1 3/4 inches long with 5 narrow, petal-like spreading lobes. The 5 stamens are extended. Fall foliage is orange to maroon.
This typical wetland shrub is sometimes called the Clammy Azalea because of its very sticky corolla. The species name means sticky in Latin. The flowers appear after the leaves. Another white wetland species of more southern distribution, the Smooth Azalea (R. arborescens), has smooth twigs, leaves without hairs, and red stamens. Dwarf Azalea (R. atlanticum), with white or pink fragrant flowers on a shrub 3-4 (90-120 cm) tall, is common in deep and along the coastal plain from southern New Jersey to South Carolina.
From the Image Gallery
Plant CharacteristicsDuration: Perennial
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Simple
Breeding System: Flowers Bisexual
Size Notes: Growing up to 15 feet tall but typically around 5 feet.
Autumn Foliage: yes
Size Class: 6-12 ft.
Bloom InformationBloom Color: White , Pink
Bloom Time: May , Jun , Jul , Aug
DistributionUSA: AL , AR , CT , DC , DE , FL , GA , LA , MA , MD , ME , MS , NC , NH , NJ , NY , OK , PA , RI , SC , TN , TX , VA , VT
Native Distribution: ME to OH, s. to FL & LA
Native Habitat: Swamps; bogs; stream margins
Growing ConditionsWater Use: High
Light Requirement: Part Shade
Soil Moisture: Wet
Soil pH: Acidic (pH<6.8)
CaCO3 Tolerance: Low
Soil Description: Wet soil.
Conditions Comments: This is one of the last azaleas to bloom in spring. It is a variable species with several varieties and forms. Good cultural practices reduce the incidence of disease and insect damage. Flood tolerant.
BenefitUse Wildlife: Low.
Warning: Rhododendrons contain poisonous substances and should not be ingested by humans or animals. Honey made from flowers also may be toxic. POISONOUS PARTS: All parts. Highly Toxic, May be Fatal if eaten. Symptoms include 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. Toxic Principle: Andromedotoxin. (Poisonous Plants of N.C.)
Conspicuous Flowers: yes
Fragrant Flowers: yes
Value to Beneficial InsectsSpecial Value to Bumble Bees
This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.
PropagationDescription: Combine seeds loosely with sphagnum moss and sprinkle lightly over a 2:1 perlite/peat mixture. Germinate under mist or a plastic tent. Optimum temperatures for germination are 45-50 degrees. Transplant seedlings to acid soil with a high content of orga
Seed Treatment: No pretreatment is necessary.
Commercially Avail: yes
National Wetland Indicator Status
From the National Organizations DirectoryAccording to the species list provided by Affiliate Organizations, this plant is on display at the following locations:
Delaware Nature Society - Hockessin, DE
Mt. Cuba Center - Hockessin, DE
BibliographyBibref 1620 - Gardening with Native Plants of the South (Reprint Edition) (2009) Wasowski, S. with A. Wasowski
Bibref 318 - Native Texas Plants: Landscaping Region by Region (2002) Wasowski, S. & A. Wasowski
Bibref 248 - Texas Wildflowers: A Field Guide (1984) Loughmiller, C. & L. Loughmiller
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Research LiteratureReslit 251 - Genetic diversity of seven deciduous azalea species (Rhododendron spp. section Pentanthera) native to the eastern United States (2008) M. Chappell, C. Robacker and T. M. Jenkins
Reslit 284 - Investigating parentage and hybridity of three azaleodendrons using amplified fragment length polymorphism analysis (2007) R. N. Contreras, T. G. Ranney, S. R. Milla-Lewis a...
Reslit 765 - Attaining inter-subgeneric hybrids in fragrant azalea breeding and the inheritance of organelle DNA (2008) N. Kobayashi, D. Mizuta, A. Nakatsuka and M. Akaba...
Reslit 945 - Development of multiplex PCR markers to distinguish evergreen and deciduous azaleas (2008) D. Mizuta, A. Nakatsuka and N. Kobayashi
Reslit 1450 - Identification of resistance to azalea lace bug among deciduous azalea taxa (1998) Y. F. Wang, C. D. Robacker and S. K. Braman
Reslit 1997 - Cold Hardiness of Various Provenances of Flame, Roseshell, and Swamp Azaleas (1991) N. E. Pellett, N. Rowan and J. Aleong
This information was provided by the Florida WIldflower Foundation.
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Additional resourcesUSDA: Find Rhododendron viscosum in USDA Plants
FNA: Find Rhododendron viscosum in the Flora of North America (if available)
Google: Search Google for Rhododendron viscosum
MetadataRecord Modified: 2017-07-07
Research By: TWC Staff