Host an Event Volunteer Join Tickets

Support the plant database you love!


Plant Database

Search for native plants by scientific name, common name or family. If you are not sure what you are looking for, try the Combination Search or our Recommended Species lists.

Enter a Plant Name:
Or you can choose a plant family:
Rhododendron viscosum (Swamp azalea)
Cressler, Alan

Rhododendron viscosum

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

USDA Native Status: L48 (N)

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

25 photo(s) available in the Image Gallery

Plant Characteristics

Duration: Perennial
Habit: Shrub
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Simple
Breeding System: Flowers Bisexual
Fruit Type: Capsule
Size Notes: Growing up to 15 feet tall but typically around 5 feet.
Leaf: Green
Autumn Foliage: yes
Fruit: Brown

Bloom Information

Bloom Color: White , Pink
Bloom Time: May , Jun , Jul , Aug


USA: 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 Conditions

Water 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.


Use 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
Attracts: Birds

Value to Beneficial Insects

Special Value to Bumble Bees

This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.


Description: 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

This information is derived from the U.S. Army Corps of Engineers National Wetland Plant List, Version 3.1 (Lichvar, R.W. 2013. The National Wetland Plant List: 2013 wetland ratings. Phytoneuron 2013-49: 1-241). Click here for map of regions.

From the National Organizations Directory

According 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


Bibref 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

Search More Titles in Bibliography

Research Literature

Reslit 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.
Search More Titles in Research Literature

Additional resources

USDA: Find Rhododendron viscosum in USDA Plants
FNA: Find Rhododendron viscosum in the Flora of North America (if available)
Google: Search Google for Rhododendron viscosum


Record Modified: 2017-07-07
Research By: TWC Staff

Go back