What is Summersweet?

Not many shrubs bloom in the dog days of late summer, but one outstanding exception is summersweet.

This colony-forming native shrub produces many upright, branching stems that are covered with narrow, upright clusters of small white or pink flowers from late July into August. The flowers have a wonderful sweet and spicy fragrance, and they attract butterflies. Summersweet has clean, glossy green foliage that develops nice yellow tones in autumn. Its spreading growth habit and love of moisture makes it ideal for plantings in rain gardens, on stream banks, and around ponds.

Common name: Summersweet, sweet pepperbush
Botanical name: Clethra alnifolia
Plant type: deciduous shrub
Zones: 4 to 9
Height: 5 to 8 feet
Family: Clethraceae

Growing conditions

  • Sun: Full sun or partial shade.
  • Soil: Moisture-retentive, acidic soil with plenty of organic matter.
  • Moisture: Evenly moist to wet; requires watering in dry spells.

Care

  • Mulch: 1 to 2 inches of organic mulch like wood chips, shredded leaves, or pine needles.
  • Pruning: Rarely needed; cut back or dig out suckers if colony size must be reduced.
  • Fertilizer: Topdress annually with compost.

Propagation

  • Seeds
  • Stem cuttings
  • Dividing root suckers

Pests and diseases

  • No major problems

Cultivars

  • ‘Ruby Spice’ has lovely rose-pink flowers.
  • ‘Hummingbird’ (shown in photo) is a compact (3 to 4 feet tall) cultivar with white flowers.
  • ‘Sixteen Candles’ is a compact (4 to 5 feet tall) and floriferous cultivar.

Garden notes

  • If butterfly bush (Buddleia spp.) is invasive in your region, summersweet may be a good substitute, although it requires moister soil conditions than butterfly bush.
  • Combine summersweet with other shade tolerant, moisture-loving plants, including winterberry (Ilex verticillata), cardinal flower (Lobelia cardinalis), and turtleheads (Chelone spa.).

All in the family

  • Summersweet is a member of the clethra family (Clethraceae), which contains only two genera.
  • Clethra species are native to parts of Asia, North America, Central America, and South America.
  • Most Clethra species grow as shrubs, but Japanese clethra (Clethra barbinervis, Zone 5 to 9) forms an attractive small tree with multi-colored bark.

Where to buy
American Native Nursery, Quakertown, PA; americannativenursery.com
Forestfarm, Williams OR; forestfarm.com
Wayside Gardens, Hodges, SC; waysidegardens.com
Woodlanders, Aiken SC; woodlanders.net