Clethra alnifolia (coastal sweetpepperbush or summersweet), is a species of flowering plant in the genus Clethra of the family Clethraceae, native to eastern North America from southern Nova Scotia and Maine south to northern Florida, and west to eastern Texas.
It is a deciduous shrub growing to 1.5–3 m (4 ft 11 in–9 ft 10 in) tall. The leaves are obovate to oblong, 4-10 cm long and 2-4 cm broad, with a serrated margin; they are green turning yellow-golden during the autumn. The flowers are white or very pale pink, 5-10 mm in diameter, and have a sweet, somewhat cloying fragrance, the flowers attractive to bumblebees; they are produced in racemes up to 15 cm long and 2 cm broad in late summer, depending on the cultivar. The "pepper" part of the common name derives from the mature fruits, capsules which have a vague resemblance to peppercorns, however, with no element of spiciness.
Sweetpepperbush is typically used as a shrub for natural gardens, or is placed alongside a stream or pond in order to delay erosion. Limiting its landscaping use is the fact that it does not leaf out until very late in the season. Several cultivars have been selected for garden use, including 'Ruby Spice', with strongly pink flowers; 'Hummingbird', for its dwarf size; and 'September Beauty'.