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Summersweet clethra

Clethra alnifolia

Common names:
summersweet clethra, summersweet, clethra, sweet pepperbush

Content Detail

A wide variety of butterflies and songbirds are attracted to summersweet clethra for its nectar and seeds. Native to the eastern United States, it provides exceptional four season interest with its lustrous green leaves in the spring, spiky white or pink fragrant summer flowers, golden yellow autumn leaves, and interesting, delicate dried seed capsules in winter.

  • Family (English) Summersweet
  • Family (botanic) Clethraceae
  • Tree or plant type Shrub
  • Foliage Deciduous (seasonally loses leaves)
  • Native locale North America
  • Size range Small shrub (3-5 feet), Medium shrub (5-8 feet)
  • Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily), Full shade (4 hrs or less of light daily)
  • Hardiness zones Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
  • Soil preference Acid soil, Moist, well-drained soil, Wet soil
  • Tolerances Alkaline soil, Occasional flooding, Road salt, Wet sites
  • Season of interest early winter, midwinter, midsummer, late summer, early fall, mid fall, late fall
  • Flower color and fragrance Fragrant, Pink, White
  • Shape or form Oval, Round, Thicket-forming, Upright
  • Growth rate Moderate, Slow

Size and form:

This shrub can grow from 3 to 8 feet with an oval, upright shape. It is thicket-forming.

Native geographic location and habitat:

It is a native to the eastern coast of the United States.

Attracts birds, pollinators and mammals:

Songbirds, including robin, goldfinch, and warblers are attracted to the seed capsules. It is a nectar source for swallowtail butterflies and hummingbirds.

Bark color and texture:

The multi-stemmed bark is brown.

Leaf or needle arrangement, size, shape, and texture:

The 2 to 4 inch, simple, alternate, sharply serrated leaves are medium to dark green above and paler beneath. It is slow to leaf out in spring. The leaves turn a golden-yellow in fall.

Flower description:

The fragrant, five-petaled flowers are in upright spikes on the end of branches. Color varies by cultivar from white to pink.

Fruit, cone, nut, and seed descriptions:

Interesting, delicate, dried seed capsules persist through winter.

Plant care:

This shrub grows best in part shade to full sun in moist to wet soils. It spreads by suckering roots forming wide colonies. Since it flowers on new wood, it can be pruned to control size in spring.

List of pests, diseases and tolerances:

There aren’t any serious problems. It is tolerant of different soil pH and aerial salt spray.

Hummingbird summersweet clethra (Clethra alnifolia ‘Hummingbird’):

A 2 to 3 feet high and wide rounded cultivar with white flower clusters that are larger and open earlier than the species.

Ruby Spice summersweet clethra (Clethra alnifolia ‘Ruby Spice’):

A 4 to 6 feet high and wide cultivar with an oval to rounded form and rosy pink flowers.

Sixteen Candles summersweet clethra (Clethra alnifolia ‘Sixteen Candles’):

This cultivar is 2 to 3 feet high and wide rounded with white flowers.

Vanilla Spice™ summersweet clethra  (Clethra alnifolia ‘Caleb’):

A 4 to 6 feet high and 3 to 5 feet wide upright to rounded form cultivar has white flowers that are larger than those of the species.

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