Clethra is a genus 75 species of flowering shrubs and small trees in the Clethraceae plant family, in the order Ericales that includes azaleas. There are two recognized species native to the US and 7 native to China. The rest come from other parts of Asia, Malesia, Mexico, Central and South America, and one species from the island of Madeira where they grow in a variety of habitats, including swamps, woodland, and rocky sites. Photo Credit: Wikipedia
Clethra may be deciduous or evergreen, grows into a shrub or small tree, and has simple, ovate leaves that are toothed and bear distinctive stellate hairs. The bell-shaped flowers are small, white to pinkish and are borne in racemes or panicles. The flowers of the selections below bloom in mid to late summer, are fragrant and attractive to bees and butterflies. The fruit is a 3-chambered seed capsule that contains numerous very small seeds. All the ones described below do well in part shade to full sun, in fertile, consistently moist, well-drained, slightly acidic soil. They prefer a sheltered position because the leaves are delicate and the plants are easily tipped over by the wind. All are generally healthy but may suffer from red spider mites in dry conditions. Propagation is by seed and stem cuttings. These six Clethra are good choices for mixed borders, and woodland, native plant, butterfly, pollinator, and fragrance gardens. Some have good autumn color and two have exfoliating bark that adds winter interest. The genus name Clethra, is from the Greek word klethra, meaning alder, and refers to the resemblance of the leaves to those of alders.
Mountain Pepperbush (Clethra acuminata)
Also known as cinnamon pepperbush, this native of the Appalachian Mountains of the southeastern US grows 8-20′ tall and has an attractive horizontal branching pattern. The leaves are 2-6″ long and are dark green before turning yellow gold in the fall. The white flowers have a honey like fragrance and are carried on 3-8″ drooping racemes. Winter interest is provided by the exfoliation of the outer bark of mature stems to reveal the cinnamon colored inner bark. Photo Credit Wikipedia
Type: Deciduous shrub or small tree
Height: 8-20′
Outstanding Characteristic/s: Autumn coloration, honey scented flowers, exfoliating bark, native plant
USDA Hardiness Zones: 6-7
Sweet Pepper bush (Clethra alnifolia)
Growing 3-6′ tall, this native of eastern US, has 4″ long racemes of white to pinkish flowers. The dark green leaves are 1.5-4″ long and turn rich golden yellow in autumn. Photo Credit Wikipedia
Type: Deciduous shrub
Height: 3-6′
Outstanding Characteristic/s: Autumn coloration, native plant, ‘Ruby Spice’ has outstanding fragrance
USDA Hardiness Zones: 4-8
Lily of the Valley Tree (Clethra arborea)
This evergreen shrub or small tree is native to the semitropical forest of Madeira. It is narrowly upright and grows about 20′ tall by 13′ wide and has dense, dark green glossy leaves that are 3-6″ long, and oblanceolate. The flowers are similar in appearance to those of lily the valley, and carried in lax panicles 3-6″ long. They are attractive to hummingbirds as well as butterflies, and are good cut flowers. Suitable for growing in a container. Photo Credit Wikipedia
Type: Evergreen shrub or small tree
Height: 20′
Outstanding Characteristic/s: Evergreen, flowers with lily-scent
USDA Hardiness Zones: 8-10
Japanese Clethra (Clethra barbinervis)
Native to the open mountain forests of southern China, Japan and Korea and Japanese clethra grows 10-20′ tall and has terminal clusters of glossy, ovate, serrated leaves that are 2-5″ long and are dark green until turning yellow to maroon or bronze red in the fall. The white flowers are carried in horizontally drooping, terminal racemes 4-6″ long and have a pleasant apple cider scent. Winter interest is provided by the polished brown to cinnamon exfoliating bark. Photo Credit : Krzysztof Ziarnek, Wkimedia Commons
Type: Deciduous
Height: 10-20′
Outstanding Characteristic/s: Autumn coloration, apple cider scented flowers, exfoliating bark
USDA Hardiness Zones: 5-8
Delavayi Summersweet (Clethra delavayi)
Growing up to 15″ tall this native of western China has lanceolate leaves that are toothed, 2.5-6″ long, and dark blue green until turning orange to red in the fall. In summer, pink buds open to sweet scented white flowers on dense, terminal, one-sided racemes 4-6″ long. Photo Credit: Wikimedia Commons
Type: Deciduous
Height: 15′
Outstanding Characteristic/s: Fall coloration, sweet scented flowers
USDA Hardiness Zones: 6-10
Chinese Alder (Clethra fargesii)
Also known as bush pepper, common white alder, nana, and pink spire, this native of the woodlands and mountains of Central China grows 6-10′ tall and has smooth, marbled brown to cinnamon bark that exfoliates. The elliptical to oblong leaves are 2-5″ long, serrated, and are borne in terminal clusters. They are dark green turning yellow to coppery and burgundy in the fall. The fragrant white flowers are carried in terminal clusters 6-10″ long and have an apple scent. Photo Credit: Agnieszka Kwiecień, Wikimedia Commons
Type: Deciduous
Height: 6-10′
Outstanding Characteristic/s: Autumn coloration, apple scented flowers, exfoliating bark
USDA Hardiness Zones: 6-9