Coastal Sweetpepperbush (Alnifolia)

The Coastal Sweetpepperbush (Alnifolia) is generally described as a perennial shrub. This is native to the U.S. (United States) has its most active growth period in the spring and summer . The greatest bloom is usually observed in the summer, with fruit and seed production starting in the summer and continuing until fall. Leaves are not retained year to year. The Coastal Sweetpepperbush (Alnifolia) has a moderate life span relative to most other plant species and a moderate growth rate. At maturity, the typical Coastal Sweetpepperbush (Alnifolia) will reach up to 16 feet high, with a maximum height at 20 years of 16 feet.

The Coastal Sweetpepperbush (Alnifolia) is easily found in nurseries, garden stores and other plant dealers and distributors. It can be propagated by bare root, container, seed. It has a slow ability to spread through seed production and the seedlings have low vigor. Note that cold stratification is not required for seed germination and the plant cannot survive exposure to temperatures below -23°F. has low tolerance to drought and restricted water conditions.

Uses of : Landscaping, Medicinal, Culinary, etc.

Erosion control: Coastal sweet pepperbush spreads by sending up new shoots, forming a thicket of low bushes. Growth from root suckering will provide moderate erosion control along streams and ponds.

Garden and landscape: The foliage and flowers of coastal sweet pepperbush make it an attractive garden shrub. It can be used in a mixed shrub hedge or border and pruned to maintain a small size. The lush green leaves turn to golden yellow in autumn. The fragrant flowers last up to 6 weeks or more during the middle of summer while other flowering shrubs are not blooming due to the heat.

Utility right of ways: Coastal sweet pepperbush is sometimes used to halt succession of tall trees along pathways. It has been planted following herbicide

application along electrical transmission, telephone, railroad, roadside, and pipeline right of ways. Its low stature does not interfere with the general operations around these utility areas.

Wildlife: The fragrant white flowers and nectar of coastal sweet pepperbush attract hummingbirds and butterflies. Deer eat it only when other forage vegetation is limited. Birds eat the fruit and aid in seed dispersal.

General Characteristics

General: White Alder Family (Clethraceae). Coastal sweet pepperbush is a large deciduous shrub that grows to 2.5 m tall. The bark is smooth, reddish-orange or gray in color, and 2 to 3 mm in diameter. Twigs are reddish-orange covered with dense white hairs. Leaves are alternate, simple, 5 to 8 cm long, and toothed toward their tips. They are medium to dark green, turn golden yellow in the fall and have appressed white hairs along the midvein. Flowers are up to 1 mm long and 0.8 mm wide, composed of 5 white fused petals. Seventeen to one hundred fragrant flowers form the bottlebrush-like inflorescences that are about 10 cm long and 2 cm wide. The fruiting stalk has many miniature oval 3-seeded capsules that are winter-persistent and are good identification features. Coastal sweet pepperbush produces leaves in late spring, flowers in July and August, and sets fruit in September and October. The yellow fall foliage persists for two to four weeks.


Coastal sweet pepperbush is listed as a special concern species in Maine and as threatened in Tennessee.

General Upkeep and Control

Legginess occurs with age among coastal sweet pepperbush plants. Aggressive root suckering also occurs with age which is an asset if naturalization or moderate erosion control is desired.

Coastal sweet pepperbush can build up and create a fire hazard. It can be controlled with regular prescribed burning. Most fires probably top-kill sweet pepperbush, but the plant can resprout from surviving stolons. Fires severe enough to consume the organic soil may kill stolons.

Pests and Potential Problems Damage caused by spider mites can be severe on plants in hot, dry locations.

Seeds and Plant Production Coastal sweet pepperbush can be propagated by seeds, summer cuttings, or sucker division. Seeds are cold stratified for 30 days and germinated under spring temperatures.

Collect 10 cm long softwood cuttings at the end of May or the beginning of June and strip the leaves from the lower two-thirds of the cutting. Wound the lower portion of the stem and apply a powder or liquid root hormone compound. Place cuttings in coarse sand that is 7 to 10 cm deep and lightly water at least every 2 hours. The medium can be any well-drained mixture that does not contain soil. Provide shade to the cuttings for the first 7 to 10 days to allow the cuttings to harden off before exposing them to full sun. For best rooting results, place cuttings in an intermittent misting system.

Plant Basics
Growth Rate Moderate
General Type Shrub
Growth Period Spring, Summer
Growth Duration Perennial
Lifespan Moderate
Plant Nativity Native to U.S.
Commercial Availability Routinely Available
Physical Characteristics
Bloom Period Summer
Displays Fall Colors No
Shape/Growth Form Multiple Stem
Drought Tolerance Low
Shade Tolerance Intermediate
Height When Mature 16
Vegetative Spread Slow
Flower Color White
Flower Conspicuousness No
Fruit/Seed Abundance Low
Fruit/Seed Seasonality Summer Fall
Seed Spread Rate Slow
Gardening Characteristics
Propagations (Ways to Grow) Bare Root, Container, Seed
Moisture Requirements High
Cold Stratification Required No
Minimum Temperature -23
Soil Depth for Roots 16
Toxic to Nearby Plants No
Toxic to Livestock No
After-Harvest Resprout Ability No
Responds to Coppicing No
Growth Requirements
pH Range 4.5–7 pH
Precipitation Range 35–35 inches/yr
Planting Density 700–1700 indiv./acre
Soil Textures Coarse, Medium
Soil Depth for Roots 16
Minimum Frost-Free Days 150 day(s)
Salinity Tolerance None
CaCO3 Tolerance Low
Sustainability & Use
Leaf Retention No
Palatability Medium
Fire Resistant No

Source: USDA, NRCS, PLANTS Database,
National Plant Data Center, Baton Rouge, LA 70874-4490 USA