Summersweet, Clethra alnifolia

February 26, 2020

By Matt

Did You Know?

Summersweet is also called sweet pepperbush for its peppercorn-like seeds!

Snapshot


  • Summersweet (Clethra alnifolia) is a medium-sized deciduous shrub. It typically grows in a round or oval shape about 3 to 6 feet high and 4 to 6 feet wide. In spring, the leaves are glossy and deep green, 2 to 4 inches long, with serrated edges. Foliage turns gold in fall.
  • In summer, the shrub is covered with long spikes of fragrant white or pink flowers. After blooming, brown seed pods develop, and these remain in place through winter, providing food for songbirds.
  • It spreads slowly via suckering roots and can form wide colonies
  • Summersweet is native to the wet marshes, coastal areas, stream banks, and woodlands of eastern North America. It can be found along the Atlantic coast and as far southwest as Texas.

Cletha ‘Hummingbird’ Flowers
Credit: https://www.monrovia.com/plant-catalog/plants/907/hummingbird-summersweet/

What Makes Summersweet So Awesome?

Summersweet thrives in wet and shady areas, so it’s good for woodland and rain gardens, and naturalizing. It spreads slowly enough to be manageable but, when allowed to, will sucker freely and form dense mounds or natural hedges.

It requires little care, but is attractive in every season:

Spring—attractive foliage and dense branches make summersweet a good border plant or privacy screen.

Summer—beautiful, deeply fragrant blooms are an important native nectar source for butterflies, bees, and hummingbirds. Summersweet blooms even in shade.

Autumn—uniform golden-yellow foliage makes this a standout in the fall garden.

Winter—interesting seed pods attract robins, goldfinches, warblers and other songbirds.

How Can I Grow One?

Summersweet is extremely tolerant of less-than-ideal growing conditions, as long as its soil remains evenly moist. It does best in full sun to part shade, but will tolerate full shade. It prefers soil that is sandy and slightly acidic, but can be grown in clay soil. It will tolerate wet areas, even occasional seasonal flooding, and coastal salt spray as well as road salt.


Clethra ‘Ruby Spice’ Flowers
Credit: https://www.whiteflowerfarm.com/60983-product.html
It’s slow to leaf out in spring, so it’s good to pair summersweet with ferns, sedges, or other plants that offer early visual interest.

Summersweet has no serious problems with insects or disease, but may be troubled by spider mites, especially if plants dry out.

Feed with slow-release fertilizer in spring, and deadhead blooms occasionally; otherwise, summersweet requires little care during the growing season. 

It flowers on new wood, so prune in late winter, removing about a third of the longest stems at ground level to encourage new growth. Also trim to control size and remove any dead

In addition to its spread via root sprouts, summersweet can be easily propagated from cuttings.

Types to try: ‘Hummingbird’ a compact cultivar with white bloom spikes. Reaching only 3 to 4 feet tall, it’s perfect for small gardens and large containers.

‘Ruby Spice’ has spikes of deep rose-pink buds that open into creamy pink-edged flowers. It grows to about 4 to 6 feet tall and slightly wider.

Summersweet grows in Zones 4 through 9.

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