Flower profile

Swamp loosestrife

Decodon verticillatus

Swamp loosestrife (Decodon verticillatus) is a shrub in the Lythraceae family, native in the lower 48 states, blooming mostly July–September across the U.S.

Native to Rhode Island

Swamp loosestrife is a flowering plant that USDA PLANTS lists as native in the lower 48 states.

32states where USDA records it

161RI sightings*

7,848U.S. sightings*

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

On our lists for: Rhode Island

Quick look

Decodon verticillatus, the sole living species in the genus Decodon, is a flowering plant in the family Lythraceae. It is commonly known as waterwillow or swamp loosestrife. It is native to wetlands in the eastern half of the United States and Canada.
From Wikipedia's article Decodon verticillatus, CC BY-SA 4.0.

It belongs to the Lythraceae family. ^iNaturalist
USDA PLANTS describes it as a shrub / a subshrub with a perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as native in the lower 48 states and records it in 32 states. ^{USDA PLANTS}
NatureServe lists it as native to Rhode Island. ^NatureServe
USDA PLANTS lists its flower color as red. ^{USDA PLANTS}
USDA PLANTS gives its bloom period as mid summer. ^{USDA PLANTS}
USDA PLANTS lists a mature height of about 8 ft. ^{USDA PLANTS}
iNaturalist has 161 research-grade sightings of it in Rhode Island, ranking #99 among the 164 flowers on our Rhode Island list. ^iNaturalist

When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (577 records)

There are only a handful of Rhode Island flowering records, so this chart uses records from across the U.S.

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
Rhode Island: Not listed Not on Rhode Island Rare Plants 2016 (RI Natural History Survey, from the RI Wildlife Action Plan; informational, Rhode Island has no state plant-protection listing law). NatureServe: SNR, not yet ranked in Rhode Island. ^{RI rare plants 2016}
Rare elsewhere: Other states where NatureServe ranks it rare or missing: IA (S1), MO (S1), MS (S2), WV (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 page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.

For petsNot well documented

It isn't on the ASPCA plant list.

🌿 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 swamp loosestrife in 32 states plus Washington, D.C.

AKMEVTNHWAIDMTNDMNILWIMINYRIMAORNVWYSDIAINOHPANJCTCAUTCONEMOKYWVVAMDDEAZNMKSARTNNCSCDCOKLAMSALGAHITXFL

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Vermont, Virginia, West Virginia, Wisconsin; District of Columbia.

Rhode Island counties with USDA records: Newport, Providence, Washington.

Growing conditions

USDA PLANTS gives Swamp loosestrife a medium shade tolerance, none drought tolerance and high moisture use. It is rated for soil pH 4.9 to 8.6 and winter lows down to -23 °F.

Shade tolerance: Medium
Drought tolerance: None
Moisture use: High
Soil textures it is adapted to: coarse, medium, fine
Soil pH range: 4.9 to 8.6
Minimum temperature tolerated: -23 °F
Frost-free days needed (minimum): 145
Annual precipitation range: 30 to 60 inches
Minimum root depth: 10 inches
Salinity tolerance: None
Fertility requirement: Medium
Growth rate: Rapid
Lifespan: Long
Active growth period: Summer and Fall
Fruit or seed: Brown · Summer to Fall
Can be propagated by: bare root, container, cuttings, seed
Commercial availability: Routinely Available

From the USDA PLANTS characteristics data for DEVE. 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.

County records: USDA PLANTS lists it in 452 counties across 30 states; the most are in Michigan (45), New York (43), Ohio (34).

More from the Lythraceae family (3 on Bloomipedia; most observed first): Purple loosestrife, Winged loosestrife, Crape myrtle.

More Rhode Island flowers

Purple loosestrife

Lythrum salicaria

Introduced

🌼 Few flowering records in RI

Crape myrtle

Lagerstroemia indica

🌷 Flowering tree

🌷 Grown in Rhode Island gardens

Roses (genus Rosa)

Rosa

★ NY state flower🌷 Garden flower

🌼 Blooms in RI: June–August

Sources

USDA, NRCS. PLANTS Database, profile DEVE.
iNaturalist, Decodon verticillatus: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
Wikipedia, Decodon verticillatus (lead quoted under CC BY-SA 4.0).
Rhode Island: Rhode Island Rare Plants 2016 (RI Natural History Survey, from the RI Wildlife Action Plan; informational, Rhode Island has no state plant-protection listing law).
USFWS, ECOS species database (ESA listing check), October 17, 2026.
NatureServe Explorer, Decodon verticillatus (global and state ranks).
Edibility and toxicity: no source found (marked "not well documented").
Photo: Lucy Keith-Diagne via iNaturalist · CC BY 4.0 · resized.