Learn how to grow clethra or pepperbush including the best varieties.
Listen to podcast:
How to Grow: Pepperbush
Clethra alnifolia
KENPEI
Other Name
Summersweet
Sun Requirements
full sun, part sun, part shade
Bloom Period and Seasonal Color
Mid to late summer with white or pink flowers and yellow fall foliage color
Mature Height x Spread
5 to 8 feet x 4 to 6 feet
Added Benefits
attracts beneficials, native, fall color
This common, native shrub is often found in moist woodland areas because it tolerates part shade and moist soils well. Pepperbush is a multi-stemmed, rounded shrub that is slow to leaf out in spring. Often gardeners will think it has died, only to see their pepperbush covered with leaves a week or so later. One thing I like about pepperbush is it blooms in mid to late summer when few other shrubs are flowering. And the white or pink flowers are shaped like candles and are very fragrant. It’s a great shrub to grow close to a deck, patio or window to enjoy the scent. In fall the foliage turns a golden color adding to the multi-season interest.
When, Where and How to Plant
Pepperbush is hardy throughout New England. Purchase plants from a local garden center or take divisions from a neighbor or friend’s plant. Plant shrubs from spring to early fall in well-drained, moist soil in a part sun or shade location. Pepperbush grows best in humus-rich, slightly acidic soils that don’t dry out. Space plants 4 to 6 feet apart.
Growing Tips
Keep pepperbush soil moist by watering regularly and mulching with pine needles or evergreen bark mulch to keep the soil slightly acidic. Fertilize in spring with an organic plant food.
Regional Advice and Care
Pepperbush may have some twig dieback after the first winter, but otherwise grows well in our climate. Pepperbush forms flowers on the new growth so prune the shrub in spring to promote new growth and shape the plant. Remove dead, diseased and damaged branches at any time. Pepperbush suckers freely. Prune out crowded new growth or dig up and divide the main bush to create new shrubs. Pepperbush has few pests. Protect plants from deer and rabbit browsing by erecting a barrier of burlap, wire or wood in late fall.
Companion Planting and Design
Plant pepperbush as a foundation plant where it won’t block a window, door or walkway. Plant it close to the house and windows so you can enjoy the fragrant flowers in summer. Pepperbush also looks great in a mixed shrub border with earlier blooming potentilla and dwarf spirea or in a hedgerow where it will sucker freely and fill in the space. To add color in mid summer, plant pepperbush in the back of a perennial flower border with other mid summer bloomers such as daylilies and bee balm. Pepperbush is also tolerant of salt spray so can be planted near the ocean.
Try These
‘Hummingbird’ grows 3 to 4 feet tall and wide and has good fall foliage color. ‘Ruby Spice’ has dark pink flower buds that open to light pink and don’t fade. It also has dark glossy foliage. ‘Creel’s Calico’ grows 5 feet tall with variegated white and green leaves.
Excerpted from my book, New England Getting Started Garden Guide.
Podcast Transcript
I like a shrub who’s description says it tolerates shade, clay soil, wet soil and erosion and still flowers. This shrub is called the pepperbush or summersweet. It’s botanical name means “alder” in Greek since the leaves resemble those of the alder tree. We call it clethra.
Not only is clethra a tough, native shrub that grows 3 to 6 feet tall and wide it’s tolerant of wet soils and shade. It’s unique in that it’s flowers now, when few other shrubs flower and blooms in shade. The sweet smelling blooms are white or pink depending on the variety and flower from mid summer till fall. Butterflies and bees love this shrub so it’s a good one for pollinator gardens. Because of its versatility, clethra can be planted in many spots in your yard. Plant it in part shade along the house as a foundation plant, in full sun in a hedgerow with other shrubs or along a stream or pond for erosion control.
Clethra is hardy to zone 4 and has a number of newer varieties. ‘Hummingbird’ and ‘Sixteen Candles’ are more compact growing selections reaching only 3 feet tall and wide. The flowers have a sweet, clove-like scent. ‘Pink Spire’ and ‘Ruby Spire’ have colorful flowers that also have a strong fragrance. Cinnamon clethra is only hardy to zone 5, but produces brilliant, golden fall foliage.
Clethra tolerates a range of soils, but needs constant moisture to grow best. After planting, mulch well and keep the shrub well watered the first year. Clethra blooms on new growth, so prune in spring to remove older branches and errant shoots. This will stimulate the production of new stems and more flowers in summer.
From the Vermont Garden Journal on Vermont Public Radio.
