Summersweet is a medium-sized deciduous shrub that adds color and fragrance to your garden with its late-summer blooms. The flowers are notable for their size, how late they bloom, and their ability to bloom even in the shade. Summersweet is a versatile shrub that thrives in most climates and is suitable as a specimen plant or a hedge. It also attracts hummingbirds, bees, and butterflies.
This shrub usually grows to 3 to 6 feet in height, but can be up to 8-feet tall. Summersweet typically spreads to 4 to 6 feet and forms an oval shape. Some varieties are shorter than average for the species. Plant summersweet in the spring.
Slow-growing summersweet's leaves are obovate and serrated, 1 1/2- to 4-inches long, and change from a glossy dark green in summer to yellow or brown in the fall. Make sure there are other plants around, as the plant will look bare until the leaves appear at the end of spring. The blooms are raceme flowers, 2- to 6-inches long, that may be white, pink, or rose-colored and have a sweet fragrance. After the bloom, the flowers leave small, dark brown seed capsule fruits that look like peppercorns. These may survive into winter in some climates.
|Botanical Name||Clethra alnifolia|
|Common Name||Summersweet, sweet pepperbush, clethra, coastal sweet pepperbush, poor man's soap|
|Plant Type||Deciduous shrub|
|Mature Size||3-8 ft. tall, 4-6 ft. wide|
|Sun Exposure||Full sun, part shade|
|Soil Type||Loam, clay, sand|
|Soil pH||Acidic, 5.0-7.0|
|Flower Color||White, whiteish-pink, pink, rose|
|Hardiness Zones||3-9 (USDA)|
|Native Area||Eastern and Southern United States|
The Latin name for summersweet is Clethra alnifolia. The plant belongs to one of only two genera in the Clethraceae (white alder) family, with Purdiaea being the other genus.
Summersweet can tolerate salty air and even salt spray from nearby streets in urban areas. Its branches are dense, making it suitable for hedges or privacy screens (best in summer, of course). Being a water-loving plant, it works well at the edges of ponds, streams, and marshy areas. Elsewhere, summersweet looks nice when grouped in planting beds or lined up as a shrub border.
Plant summersweet in an area that receives full sun to part shade. An area with morning sun and afternoon shade is ideal.
This plant can work in a variety of soil pHs, types, and moisture levels. It prefers acidic, sandy soil that is moist but will tolerate clay soils, as long as they're amended with organic material, and full shade. Water regularly as needed so the soil does not dry out.
Summersweet prefers moist soil and even grows well in areas with standing water.
Temperature and Humidity
Summersweet thrives in moist climates, and tolerates both heat above 100 degrees Fahrenheit and freezing cold winters. It is originally from eastern and southern North America, but grows naturally along the Atlantic coast and west to Texas. Its natural environment includes wet and swampy areas of woodland as well as marshes and river banks.
In early spring, fertilize your summersweet with a slow-release formula meant for trees and shrubs.
- 'Creels Calico': features dark, green leaves with splotches of creamy white
- 'Crystalina': offers fragrant, white blooms
- 'Hummingbird': boasts a compact size and fragrant flowers
- 'Pink Spires': has long clusters of pink flowers, and leaves that change color in the fall
- 'Rosea': displays salmon-hued flower spikes that fade to pinkish-white
- 'Sixteen Candles': flashes long, white spikes of flowers and deep green leaves
You can deadhead to remove flowers past their prime, but otherwise, you can usually just leave this shrub alone unless you desire a neatly groomed look.
Softwood stem cuttings, taken in early summer, are the best way to propagate summersweet. Use clean garden shears to cut 3- to 4-inch cuttings, taken in the morning, from well-established healthy plants. Remove lower leaves on the cuttings, dip the ends in rooting hormone, and tuck into a mixture of half perlite and half potting soil. Keep in a high-humidity area, and cover with plastic. Once roots are established—at least five weeks, but likely longer—you can bring your cuttings outside to plant in your garden.
How to Grow Summersweet From Seed
Summersweet seeds are easy to plant and they germinate quickly; seeds can be harvested in autumn and have no specific storage needs. They can be planted immediately, or the following spring. To do so: Fill seeding trays or pots with moist potting mixture, and press the seeds in so they are halfway-buried. Cover with a thin layer of sand, then keep them in low light under plastic. Water seedlings as needed, then plant when they're sturdy. There's no need for cold stratification to germinate.
Use a 3-inch layer of organic mulch to protect your summersweet in the winter. Once spring comes, you can rake it away.
The only common problems that this shrub faces are spider mites. Control can be as simple as spraying the leaves (front and back) with water to knock them off, though further intervention with horticultural oils may be needed if mites are persistent.