Vascular Plants of North Carolina
Account for Sweet Azalea - Rhododendron serrulatum   (Small) Millais
Members of Ericaceae:
Members of Rhododendron with account distribution info or public map:
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Section 6 » Family Ericaceae
Author(Small) Millais
DistributionEssentially just the Coastal Plain, and found primarily in the Sandhills and sparingly eastward to Onslow County. A specimen for Rockingham County in the northern Piedmont (mapped by RAB) is highly suspect and needs checking. Note that Weakley's range description for this species states that the occurrence R. serrulatum in NC and SC is "uncertain." He probably means that the known county distribution is uncertain or not well worked out.

This recently split species, from R. viscosum, has a much more restricted range than that species -- occurring north only to southeastern VA, south to central FL, and west to LA.
AbundanceCommon in the Sandhills. Abundance farther eastward is not as certain, owing to confusion with R. viscosum. However, perhaps uncommon to locally fairly common in areas with wet savannas eastward to Onslow County. Seemingly absent in the northern Coastal Plain, but as it occurs in southeastern VA, it ought to be found in this region at least sparingly. Extremely rare in the Piedmont, if correctly identified.
HabitatThis is a species of acidic Coastal Plain wetlands, especially prominent in Sandhills streamhead ecotones and seepages. It also grows in wet savannas. Apparently it is found in somewhat more acidic soils in the Coastal Plain than is R. viscosum.
See also Habitat Account for Coastal Plain Wet Acidic Shrublands
PhenologyBlooms slightly earlier than the similar R. viscosum -- in late May and June (as opposed to June and July for R. viscosum). Fruits from July to October.
IdentificationThis is a deciduous shrub that grows from 2-6 feet tall (reportedly taller but those plants likely confused with R. viscosum), often in dense stands in Sandhills pocosins. The height of plants is short because recurring fires keep them so, unlike plants of R. viscosum which usually inhabits wet swamps. As with R. viscosum, it has quite shiny, elliptical, dark green leaves, with very fragrant white flowers. The inside of the corolla tube is glabrous in this species, as opposed to pubescent in R. viscosum. This character isn't visible without opening a flower, but the flower tube is greater than twice as long as the five lobes; in R. viscosum, the tube is less than twice as long as the lobes. Also, the winter buds of R. serrulatum have 15-20 scales, as opposed to 8-12 (to rarely 15) scales in R. viscosum.
Taxonomic CommentsAs indicated above, Weakley (2018) recently has considered this taxon as a valid species. Most references have treated this taxon either as a variety of R. viscosum -- as R. viscosum var. serrulatum -- or not as a valid taxon at all, and subsumed it within R. viscosum.

Other Common Name(s)Clammy Azalea, Hammocksweet Azalea
State Rank[S4?]
Global RankGNR
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B.A. SorrieSandhills Game Land, streamhead ecotone, 19 May 2012. RichmondPhoto_natural

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