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With the summersweet clethra, you can add a spicy fragrance to the garden when other plants are not blooming. So, you can enjoy an all-season garden with fragrant white flowers.
It is a medium-sized deciduous shrub with late-summer sweet blooms and can even bloom in shady locations.
The best part is that it attracts hummingbirds 🥰, bees, and butterflies to the garden. So, add it to your garden to grow as a specimen plant, hedge, or shrub border.
Plant Name: Clethra alnifolia
Other Name: Summersweet, sweet pepperbush, clethra, coastal sweet pepperbush, poor man’s soap
Plant Type: Deciduous shrub
Native Areas: Southern and Eastern North America
Light Requirement: Full sun to part shade
Fertilizer: Slow-release fertilizer
Temperature: Adapts to different temperatures
Propagation: Stem cuttings
Growth: 3-8 feet tall and 4-6 feet wide
Soil Type: Loamy clay soils
USDA Hardiness Zones: 4-9
More About Clethra Alnifolia
The flowering shrubs’ summersweet will add color and fragrance to swampy woodlands, wild gardens, and other naturalized areas. The flower buds, when open, smell like vanilla spice and can bloom in even shade.
The densely branched shrub grows up to six feet tall, and some can reach eight feet tall. It spreads six feet wide to form an oval shape. You can find some varieties that typically grow shorter. The best time to plant summersweet clethra is in spring.
These plants can grow in large colonies along stream banks in wet soil to low-lying areas. It can tolerate salt spray and also adapts well to smaller gardens. When the flowers open, they display as raceme flowers up to six inches long.
You find them with rose-colored, pink buds, or white flowers. The leaves are slow-growing and ovate to serrated in glossy dark green in summer, turning yellow to brown, creating a fall color. Still, the lustrous green leaves are a highlight in spring with the late summer blooms.
Once the blooms fade, they develop dark brown seed capsules that look like peppercorns.
‘Creels Calico’: the shrub features dark green leaves that are dark with splotches of creamy white
‘Crystalina’: with this plant, you get white flowers with the same spice fragrance with golden brown foliage in the fall.
‘Hummingbird’: the plant has a compact size with fragrant white flowers.
‘Pink Spires’: the plant forms clusters of pink blooms with foliage changing color.
‘Rosea’: the salmon-hued flower spikes are a standout on this plant, fading to pinkish-white
‘Sixteen Candles’ has long white spikes with many flowers and deep green foliage.
The Clethra alnifolia belongs to two genera found in the white alder Clethraceae family, the other being the Pudiaea genus. These hardy plants can grow in cottage gardens, or you can grow them in coastal gardens to tolerate salty air or salt spray. Depending on your variety, you can have pure white flowers that stand out on shrub borders.
Still, to add to the benefit, it is a water-loving plant that thrives in wet soils.
Clethra Alnifolia Lighting Needs
Plant summersweet clethra in full sun with part shade to receive morning sun with afternoon shade. When in bloom, you will see them attracting hummingbirds and other pollinators to the garden.
Clethra Alnifolia Soil Needs
The summersweet clethra can grow in different soil types with moist soil, but it prefers sandy soil on the acidic side. It can tolerate clay soil, but you need to amend it with organic matter and grow it in full shade. The important thing is to keep the root ball moist and not dry out.
To retain moisture, you can add some organic material as a mulch around the plant.
Watering Summersweet Clethra
Water regularly when you live in areas experiencing hot days not to allow the roots to dry out. Summer Sweet typically grows in wet soil and even adds winter interest to the garden when not in full bloom.
Temperature and Humidity
Clethra alnifolia thrives in moist soils and can tolerate heat above 100°F to cold winters. When growing in a natural environment, it can grow in wetlands, swamp areas, river banks, and marshes.
Fertilizing Clethra Alnifolia
You can feed your summersweet clethra in early spring with a slow-release fertilizer for shrubs and trees.
Pruning Clethra Alnifolia
You only need to deadhead the spent flowers and can leave the shrub to be. You can also promptly remove root suckers to keep them neatly groomed.
Propagating Summersweet Clethra
You can propagate your plant in early summer using stem cuttings or sowing seeds in early fall or spring. The best time to take softwood cutting is in early summer for rooting success.
Take four-inch stem cuttings in the morning.
Remove the lower leaves and dip the cutting in a rooting hormone.
Prepare a container with half potting soil and half perlite.
Moisten the soil and place the cuttings in it.
Cover them with clear plastic to provide high humidity.
After five weeks, the roots should be established, but it can take longer.
Once you see new growth, you can transplant them into the garden.
How to Grow Summersweet From Seed
The seeds from Clethra alnifolia germinate fast, and you can harvest them in early fall and need no storage. You can plant them in the fall or the following spring. Fill seedling trays with moist soil and bury them halfway in the soil.
Cover with a thin ground layer and keep them in indirect light under a plastic bag. Water them, and when the feelings are sturdy, you can transplant them to the garden.
Common Pests and Diseases
The only problem you will have with your plant is spider mites. You can control them using a water spray to knock them off the foliage. Or use horticultural oil to spray the foliage.
Frequently Asked Questions
Compared to a few other shrubs, the plant can reach three to 8 feet tall and up to six feet wide.
No, the plant cannot handle drought, and the roots must always remain moist.
No deer do not enjoy munching on the leaves of the summersweet clethra, but it will attract pollinators to the garden.
The plant spreads with root suckers to form large colonies with expansive growth, but it is not too invasive, and you can control it by removing the suckers when you see it.
As the plant blooms on new growth, you can prune them back in winter or early spring, as it will not affect the summer bloom.
While mostly pest-free late-season rainfall can infect the foliage with leaf spots, you can use a fungicide spray if needed. We recommend raking away fallen leaves around the plant.