Native Plant Highlight: Sweet Pepperbush

Clethra alnifolia growing as a thicket, giving the illusion of a solid border.

Native Plant Highlight: Sweet Pepperbush / Clethra alnifolia

Article by: Katie Antczak katie.antczak@gnps.org

“Grab one or two of these leaves, crush them up, add water, and scrub between your hands as fast and as hard as you can” are words often spoken by naturalists throughout the Okefenokee Swamp. One of the many amazing properties of Clethra alnifolia, also known as sweet pepper bush, summersweet, poor man’s soap, soap bush, and more, is its natural ability to make foam that resembles soap after the leaves are crushed and lathered.

This property was useful for swampers of the 19th and 20th centuries and continues to spark joy in the hearts of Okefenokee Swamp visitors today. Although the foam has no antibacterial properties, it is handy for removing smelly scents, such as fish, from hands. It’s also a lot of fun to experience!

The "soap" from the wet, crushed and scrubbed leaves of Clethra alnifolia

Late season Clethra alnifolia bloom with developing fruits in the Okefenokee Swamp

Photo: Katie Antczak

Clethra alnifolia is native to eastern North America from Nova Scotia to northern Florida and west to the eastern portions of Texas. It is most frequently found in swamps, damp thickets, sea shores, stream banks, hillside bogs, and sandy woods.

Clethra alnifolia grows well in moist, acidic soils including sands and clays. This shrub is also a facultative wetland plant, meaning that its presence indicates a site is a wetland.

Cypress, Atlantic white cedar, coastal pine species, red maple, magnolias, and beech are tree species that are usually found growing nearby. Clethra alnifolia is in the white alder (Clethraceae) family, and it is the only species in its genus that is native to North America. Although it is common in Georgia, it is listed as a species of conservation concern in some areas of its range.

Flowers of Clethra alnifolia are white or very pale pink, slender, and cylindrical spikes and form dense clusters at the end of the branch. Collectively, the bottle brush shape of the flowers are quite showy when in full bloom in the late summer, making them conspicuous when surrounded by other shrub species. Leaves are produced in late spring, flowers in July and August, and fruits ripen in September and October.

Clethra alnifolia blooms during the Great Georgia Pollinator Census in 2022

Photo credit: Katie Antczak

Clethra alnifolia blooms during the Great Georgia Pollinator Census in 2022 Photo: Katie Antczak

Other key identifying characteristics of Clethra alnifolia are the leaves and the bark. The simple and oval-shaped leaves of the bush are finely serrated and arranged alternately on the stems, and the midvein has appressed white hairs. In the fall, the leaves turn dull yellow to rich golden yellow or orange.

The bark is reddish-orange or gray and has loose stripes. The twigs are also reddish-orange and are covered in white hairs. The branches may be densely clustered when the shrub is found in thickets or mixed shrubs. The entire shrub may reach up to 2.5 m tall.

This shrub is hardy and typically resistant to insect and disease damage and physiological issues. It is also tolerant of salt-spray which makes it an ideal candidate for coastal gardens. The best zones for growth are Zones 4-9. It prefers full sun to partial shade with moist soils but with proper care may thrive in drier areas if kept moist. A potential issue in hot, dry locations is spider mites which damage the leaves of plants.

Two of the most popular cultivars are Vanilla Spice and Ruby Spice, which are chosen for their larger flowers, overall size, fragrance, and color. Other cultivars include Hummingbird, Paniculata, Pinkspire, Rosea, September Beauty, Sherry Sue, Sixteen Candles, and White Doves.

Because it can form dense thickets, the naturally growing plant and the cultivars are often used to create a hedge or border for landscaping. In moist areas the plant can be left to naturally grow into thickets through the suckers that it produces, but italso responds to pruning in the spring. Flowers willdevelop on the new wood that grows post-pruning.

By the end of November, these fruits will turn brown and be ready for wildlife consumption

Photo credit: Katie Antczak

Clethra alnifolia has a sweet scent that is oftendescribed as spicy and quite fragrant. When foundgrowing in large clusters, the scent travels andcan be smelled before actually seeing the shrub.The flowers are a particular favorite of pollinatorssuch as native bees, butterflies, wasps, flies, andeven hummingbirds. After flowering, fruit forms assmall brown capsules which remain throughout thewinter.

The fruit’s persistence through the colder monthsmake it a popular forage source for seed-eatingmammals and birds when other food sources aremore scarce. The dense thickets that it can createprovide a great refuge for migratory songbirds andother wildlife. However, Clethra alnifolia is tolerant of deer browse, so it does well in areas where theremay be a large number of deer.

In order to propagate Clethra alnifolia, take cuttings from softwood or collect the seeds. Cuttings should be taken at the end of May or the beginning of June, and leaves should be removed from the bottom two-thirds of the cutting. The lower portion of the stem should be wounded to apply a powder or liquid hormone compound, then placed in coarse sand that is watered every two hours, preferably with an intermittent misting system.

Seeds should be collected in the fall and sown on sand. The USDA suggests that the seeds should be cold stratified for 30 days and germinated under spring temperatures.

Clethra alnifolia is readily available via local nurseries and online. You can find local nurseries by visiting the Georgia Native Plant Society website at https://gnps.org/georgias-native-plants/sources-native-plants/. Definitely give the 2021 Georgia Pollinator Summer Blooming Plant of the Year a try. You won’t regret it seeing all of the pollinators that visit!

References

https://www.wildflower.org/plants/result.php?id_ plant=clal3

https://plants.ces.ncsu.edu/plants/clethra-alnifolia/

https://www.gardenia.net/plant/clethra-alnifolia

https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_clal3.pdf

https://issuu.com/statebotanicalgardenga/docs/ pollinatoryear2021