While most trees and shrubs bloom in spring, summersweet clethra (Clethra alnifolia) blooms in mid to late summer. The fragrant, white flowers are borne on 2- to 6-inch-long, bottlebrush-like spikes (racemes). The glossy foliage of summersweet clethra is medium to dark green. Fall leaf color is rather inconsistent, but in good years can range from pale yellow to golden brown. It grows 4 to 8 feet tall with an equal or slightly greater width.
Several excellent varieties are available. 'Hummingbird' is a compact cultivar which grows 3 to 4 feet tall. It has glossy green foliage and produces white flowers on 6-inch-long flower spikes. Pink flowering cultivars are also available. 'Rosea' produces pale pink flowers that fade to white as they age. 'Ruby Spice' produces bright pink, non-fading flowers on 4-foot-tall plants.
In the home landscape, summersweet clethra can be utilized as a specimen plant or placed in a mixed shrub border. Plant the shrub near a deck or patio to enjoy its fragrant flowers. Plants perform best in moist, slightly acidic soils that are high in organic matter. Summersweet clethra doesn't tolerate dry sites. During prolonged dry periods, plants may need to be watered occasionally. The shrub grows well in partial shade to full sun. Plants are hardy in USDA Hardiness Zones 3 to 8. It is generally free of insect and disease problems.
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