Photo: Averater, CC BY 4.0 · Wikimedia Commons

Cinnamon Clethra

Clethra acuminata

Also called mountain sweet pepperbush, mountain pepperbush, cinnamonbark clethra.

Peeling cinnamon-red bark and drooping spikes of spicy, fragrant white flowers in summer, on a tall shrub of Appalachian mountain slopes.

Showy flowersFall colorWildlife valueTolerates shade

Type: Shrub
Mature height: 8–20 ft
USDA zones: 6–7
Growth rate: Medium
Sun: Full, Part, Shade
Soil moisture: Dry, Average
Grows wild in: The Appalachians, rich moist slopes, rocky ground and the forest understory
Native range: 9 states, north and east to Pennsylvania, south to Georgia and west to Alabama
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Alabama, Georgia, Kentucky, North Carolina, Pennsylvania, South Carolina, Tennessee, Virginia and West Virginia
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Cinnamon clethra is the mountain cousin of our sweet pepperbush, a tall shrub or small tree of the Appalachian mountains. As it ages, its outer bark peels away to show cinnamon-red bark beneath, which gives the plant its name. It grows far taller than sweet pepperbush, blooms a little earlier, and has leaves that taper to a long point. Pennsylvania lists it as endangered, and Alabama ranks it critically imperiled. Grow it as a specimen where its bark can be seen up close, or as an understory tree at a woodland edge.

Size, growth and what to expect

It grows at a medium pace, about a foot and a half a year in our growth estimator. It grows 8 to 20 feet tall and 4 to 6 feet wide, as a many-stemmed shrub or small tree that often suckers.

Drooping spikes 3 to 8 inches long of small, spicy-scented white flowers open from June to August, from the base toward the tip. Bumble bees find them especially valuable, hummingbirds and butterflies come to the nectar, and birds eat the seed. The leaves turn yellow to orange in fall. The brown capsules show from September, but in North Carolina clethra seed ripens only in November, long after the leaves fall.

It grows wild in the mountains from Pennsylvania to northern Georgia and Alabama. Its home is wooded bluffs, cliffs and moist ravines between about 1,600 and 4,600 feet.

How to grow Cinnamon Clethra

Cinnamon clethra grows in sun or dappled shade, and it blooms best with some sun. It wants a moist, acid soil rich in humus that drains well, and rocky ground suits it. Once established it adapts to drier sites. Set plants 5 feet apart and keep them 5 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them dormant, from leaf fall until bud swell, in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and mulch with leaves, clear of the stems. The seed is tiny and needs no chilling. Sow it on the surface of a damp mix, uncovered, at room temperature in good light under mist or a clear cover. Seedlings come up within two weeks.

Water weekly through the first two summers, since young plants die in drought before their roots are down. Deer browse it only moderately, but cage young plants where deer are common. It flowers on new growth, so prune in late winter. Train it to one trunk as a small tree, or let it grow as a clump.

Each flower carries both male and female parts, and bees are its likely pollinators, so there are no male and female plants to pair. The bees it draws can be a nuisance beside a walk or a seat. Fungal dieback and root rot sometimes affect it.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (7)

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