Clethra barbinervis aka Clethra

Clethra barbinervis, or Japanese clethra, belongs to the Clethraceae family. Its native range runs from southern and eastern China to Japan. Records also place it in South Korea. It grows in open mountain woods and disturbed woodland sites. This woody plant sheds its leaves each year. It forms a large shrub or a small tree.

Garden size varies between sources and growing sites. Most US accounts give heights of 10–20 feet [3–6.1 metres]. They give widths of 10–15 feet [3–4.6 metres]. RHS lists a smaller size of 5–8 feet [1.5–2.5 metres]. NC State also describes plants around 9 feet [2.7 metres] tall. The crown can be upright, oval, or rounded and dense. Growth is fast, though new plants may settle in slowly. Root suckers can form groups of stems around the parent. Smooth bark peels to reveal brown, grey, or cinnamon tones.

The simple leaves grow in an alternate pattern along branches. They have an oval shape and sharply toothed edges. Their dark green surfaces shine, with leaves clustering near branch tips. Autumn colours range from yellow and orange to bronze and red. Small white flowers open mainly in July and August. Some accounts extend flowering into early autumn. The scented racemes grow at the tips of new shoots. These flower clusters hang outward rather than standing straight up. Bees and butterflies visit the blooms. Brown seed capsules follow and stay on through winter.

Grow this plant in moist soil that drains well. It prefers acid soil rich in humus and organic matter. Partial or dappled shade suits it best. It also tolerates full sun, but hot, dry sites cause problems. Sources list USDA zones 5–8, with NC State extending to zone 4. RHS rates it H5 for UK conditions. Give it shelter from harsh winter winds in zone 5. Late spring frost can harm fresh growth. New plants may lose some twig tips during their first winter.

Use it as a specimen, screen, hedge, or small group. It suits woodland borders and moist ground near ponds or streams. Its flowers, autumn leaves, bark, and seed spikes provide seasonal interest. Most sources report few pest or disease problems. Spider mites can cause serious damage in hot, dry places. Seeds and softwood cuttings offer ways to raise new plants. Plants For A Future records cooked leaves as food with rice. It gives a low food-use rating and lists no known hazards. It records no known medicinal or other practical uses.