Clethra alnifolia - Summersweet
Family: Clethraceae

Hear the scientific name

Clethra alnifolia is known as a summer-flowering shrub that readily naturalizes in the border or makes a good foundation shrub. Summersweet Clethera is excellent for wet sites in partial shade.

Alternate common name: Sweet Pepperbush

F   E   A   T   U   R   E   S
  form2 form Form

-medium-sized ornamental shrub

-maturing at about 6' tall x 5' wide, forming tight colonies with age (however, the increasingly predominant cultivar 'Hummingbird' is half this size)

-upright oval growth habit ('Hummingbird' has a spreading mound growth habit)

-slow growth rate

foliage2 foliage Foliage

-medium to dark green, alternate, obovate, serrated, and somewhat late to leaf out

-autumn color is usually a clear golden-yellow and persists for 2-4 weeks


-white, shell pink, or light pink, blooming anytime from late July to early Sept. (usually in mid-Aug.), and lasting for about 3 weeks when in bloom

-inflorescences are fragrant, fine-textured, upright, about 4" long x 0.75" wide, and bottlebrush-like in appearance, attracting many butterflies and bees and a moderate quantity of hummingbirds

-inflorescences occur on the new growth of the current season


-fruiting stalks noticeable, winter persistent, and a good ID feature, but not ornamental


-light brown to tan, ascending as several stems that are sparsely-branched at the base, but having numerous lateral shoots at the very apex of the new growth

-shrubs become leggy with age, and often die back at the apical stem tips in winter

-shrubs may become stoloniferous (suckering from the roots near the base of the stems) with maturity, forming tight colonies


-not applicable

C   U   L   T   U   R   E


-full sun to full shade

-best performance occurs in partial sun to partial shade in moist to wet, acidic, fertile, organic soils, but it is rather adaptable to a wide range of conditions, including sunny sites, occasionally dry soils, soils of average fertility, soils of various pH, and winter salt spray

-cultivars are propagated by rooted cuttings, but the species form may also be propagated by seeds

-White Alder Family, with no significant diseases or pests

-often suckers with age to form tight colonies (which is good for naturalized situations)

-heavy pruning, to remove winter-killed wood, to promote compactness, or to rejuvenate, is easily accomplished without worry, as flowering occurs on the new growth of the current season


-zones 3 to 9


-native to the Eastern U.S.

U   S   A   G   E


-fragrant, fine-textured inflorescences occur in mid-summer and attract many butterflies

-tolerant of permanently moist to continuously wet sites

-winter salt spray tolerant


-legginess occurs with age

-root suckering with advanced age forms small colonies (this can be an asset if naturalization or moderate erosion control is desired)


-specimen, foundation, group planting, border, or naturalizing shrub


-medium texture in foliage and when bare

-thick density in foliage and average when bare

S   E   L   E   C   T   I   0   N   S

Varieties and Cultivars - Search OSU PlantFacts for additional plants in this species


-summer-flowering shrubs (Buddleia davidii, Caryopteris xclandonensis, Itea virginica, Hydrangea species, Philadelphus species, etc.)

-wet site tolerant shrubs (Cornus [shrub forms], Hamamelis vernalis, Itea virginica, Myrica pensylvanica, Salix purpurea, etc.)

-flowering shrubs for shady spots (Calycanthus floridus, Fothergilla gardenii, Hydrangea species, Itea virginica, Pieris japonica, Rhododendron [including Azaleas], etc.)


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