Flower profile

Sweet pepperbush

Clethra alnifolia

Sweet pepperbush (Clethra alnifolia) is a shrub in the Clethraceae family, native in the lower 48 states, blooming mostly July–August across the U.S.

Native to New Hampshire

Sweet pepperbush is a flowering plant that USDA PLANTS lists as native in the lower 48 states. In New Hampshire it's most often seen in bloom in July–August.

20states where USDA records it

537NH sightings*

21,830U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: New Hampshire

Quick look

Clethra alnifolia, the coastal sweetpepperbush or summer sweet, is a species of flowering plant in the genus Clethra of the family Clethraceae, native to eastern North America from southern Nova Scotia and Maine south to northern Florida, and west to eastern Texas. It is a deciduous shrub which grows in wetlands, bogs and woodland streams.
From Wikipedia's article Clethra alnifolia, CC BY-SA 4.0.

It belongs to the Clethraceae family. ^iNaturalist
USDA PLANTS describes it as a shrub with a perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as native in the lower 48 states and records it in 20 states. ^{USDA PLANTS}
NatureServe lists it as native to New Hampshire. ^NatureServe
In New Hampshire, most iNaturalist sightings of it in flower come in July–August. ^iNaturalist
USDA PLANTS lists its flower color as white. ^{USDA PLANTS}
USDA PLANTS gives its bloom period as summer. ^{USDA PLANTS}
USDA PLANTS lists a mature height of about 16 ft. ^{USDA PLANTS}
iNaturalist has 537 research-grade sightings of it in New Hampshire, ranking #72 among the 157 flowers on our New Hampshire list. ^iNaturalist

When does it bloom?

In New Hampshire, most flowering sightings come in July–August.

Flowering records by month in New Hampshire (iNaturalist research-grade observations marked “Flowering”) (50 records)

Conservation status

Federal (U.S. ESA): Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. ^{USFWS ECOS}
NatureServe global: G5 Secure worldwide. ^NatureServe
New Hampshire: Not listed Not on New Hampshire Official Rare Plants List (Ncr 312, eff. Jan 1, 2020). NatureServe: SNR, not yet ranked in New Hampshire. ^{NH Ncr 312}
Rare elsewhere: Other states where NatureServe ranks it rare or missing: ME (S2), TN (S1). (S1 critically imperiled, S2 imperiled, SH possibly extirpated, SX presumed extirpated.)

Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.

Can you eat it?

For peopleNot well documented

None of the sources we checked (NC State Extension (no edibility or poison notes on its page), USDA PLANTS) say whether it's edible or poisonous for people. ^{NC State Extension}

For petsNot well documented

It isn't on the ASPCA plant list, and NC State Extension doesn't flag it for pets.

🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.

Where does it grow?

USDA PLANTS records sweet pepperbush in 20 states.

AKMEVTNHWAIDMTNDMNILWIMINYRIMAORNVWYSDIAINOHPANJCTCAUTCONEMOKYWVVAMDDEAZNMKSARTNNCSCDCOKLAMSALGAHITXFL

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Alabama, Connecticut, Delaware, Florida, Georgia, Louisiana, Maine, Maryland, Massachusetts, Mississippi, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Virginia.

New Hampshire counties with USDA records: Cheshire, Hillsborough, Merrimack, Rockingham, Strafford.

Growing conditions

USDA PLANTS gives Sweet pepperbush a medium shade tolerance, low drought tolerance and high moisture use. It is rated for soil pH 4.5 to 7.0 and winter lows down to -23 °F.

Shade tolerance: Medium
Drought tolerance: Low
Moisture use: High
Soil textures it is adapted to: coarse, medium
Soil pH range: 4.5 to 7.0
Minimum temperature tolerated: -23 °F
Frost-free days needed (minimum): 150
Annual precipitation range: 35 to 60 inches
Minimum root depth: 16 inches
Salinity tolerance: None
Fertility requirement: Medium
Growth rate: Moderate
Lifespan: Moderate
Active growth period: Spring and Summer
Fruit or seed: Brown · Summer to Fall
Can be propagated by: bare root, container, seed
Commercial availability: Routinely Available

From the USDA PLANTS characteristics data for CLAL3. USDA ratings are general guidance for the species, not a guarantee for your garden.

Names, range and relatives

Native status by region (USDA PLANTS): Canada: Native; Lower 48 states: Native.

Other scientific names (synonyms in USDA PLANTS): Clethra tomentosa.

County records: USDA PLANTS lists it in 290 counties across 18 states; the most are in Georgia (44), North Carolina (44), Virginia (37).

More New Hampshire flowers

Canada mayflower

Maianthemum canadense

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🌼 Blooms in NH: May–June

Canadian bunchberry

Cornus canadensis

Native

🌼 Blooms in NH: May–July

Hobblebush

Viburnum lantanoides

Native

🌼 Blooms in NH: May–June

Sources

USDA, NRCS. PLANTS Database, profile CLAL3.
iNaturalist, Clethra alnifolia: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
Wikipedia, Clethra alnifolia (lead quoted under CC BY-SA 4.0).
New Hampshire: New Hampshire Official Rare Plants List (Ncr 312, eff. Jan 1, 2020).
New Hampshire: NH Prohibited Invasive Species List (Agr 3800, Table 3800.1).
USFWS, ECOS species database (ESA listing check), October 17, 2026.
NatureServe Explorer, Clethra alnifolia (global and state ranks).
Edibility and toxicity: NC State Extension.
Photo: Ken-ichi Ueda via iNaturalist · CC BY 4.0 · resized.