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Summersweet really is a perfect description for Clethra. Pretty pink or white flowers smell sweet like honey and bloom in July and August when most shrubs have given up on blooming. Add to that its carefree nature and you have a perfect addition to the summer garden.
Clethra alnifolia is the main species grown for gardens currently. It is native to swampy areas from Texas east to Georgia and is a great choice for wet or low-lying areas of the Portland yard. All varieties adapt to sun or shade, but need more summer water if planted in sun. They are all hardy to USDA zone 4, -40f.
The varieties we include are commonly available at Portland Nursery.
‘Hummingbird’ – White flowers in spikes up to 6” long cover the plant in mid-July. Leaves are rich green with yellow & brown fall color. It grows up to 30-36” tall, but spreads readily by rhizomes under ground forming a ‘colony’. It also tends to be top-heavy and a bit floppy.
‘Ruby Spice’ – Rose pink flowers hold their color better than other pink varieties. Clusters are 3-4” long & flowering occurs in July-August. Green leaves turn gold in autumn. Grows to 6-8’ tall & 4-6’ wide.
‘September Beauty’ – White flower spikes open two weeks after other varieties and bloom into September. Growth is dense and upright, reaching 8-10’ x 6-8’ eventually.
‘Sixteen Candles’ – This is a selection from seedlings of ‘Hummingbird’. It has the same white flowers but doesn’t have the floppy characteristic, so branching is stronger and flower spikes stand upright like candles. It also is better behaved, staying in place rather than spreading under ground. It grows a bit taller, 5’ x 5’ at maturity.
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Genus: Clethra, from the greek word klethra, meaning ‘alder’.
Common: Summersweet, Sweet Pepperbush
Origin: Native to SE United States, Mexico, Japan & China
Characteristics: Deciduous shrubs and small trees with white or pink sometimes fragrant small flowers in spikes up to 4” long. Flowers open in mid summer. Oblong serrated leaves are green in summer and turn yellow to orange in fall before dropping. Fruit in fall is a 3-valved capsule and persists into winter.
Size: Size varies between species and further depends on growing conditions. Cultivated varieties can be as low-growing as 3 feet and as tall as 20 feet. In addition to that, plants growing with some afternoon shade and moist, even wet boggy soil grow larger than plants growing in very hot & dry locations.
Culture: Clethra prefer moist acidic soil rich with organic matter and can adapt to differing light conditions from shade to sun. Species native to the US grow naturally in very wet areas making it a perfect choice for ‘problem’ areas in the landscape where water pools during the rainy season. If planted in full sun it will need supplemental water in summer.
Problems: Pest free. If not given ample water in summer leaves will burn and possibly drop. Clethra alnifolia ‘Hummingbird’ spreads vigorously by rhizomes, forming large colonies, so this is a variety that needs space and really cannot be kept in a small area.