Bloomipedia
Swamp milkweed (Asclepias incarnata)
Photo: Laura J. Costello via iNaturalist · CC BY 4.0 · resized

Flower profile

Swamp milkweed

Asclepias incarnata

Swamp milkweed (Asclepias incarnata) is a flowering plant in the Apocynaceae family, native in the lower 48 states, blooming mostly June–August across the U.S.

Native in the lower 48

Swamp milkweed is a wildflower that USDA PLANTS lists as native in the lower 48 states. It's on our flower lists for 17 states, and across the U.S. it's most often seen in bloom in June–August.

43states where USDA records it
17Bloomipedia state lists include it
39,954U.S. sightings*

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

On our lists for: Delaware, Illinois, Indiana, Iowa, Maryland, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, South Dakota, Wisconsin

Quick look

Asclepias incarnata, the swamp milkweed, rose milkweed, rose milkflower, swamp silkweed, or white Indian hemp, is a herbaceous perennial plant species native to North America. It grows in damp through wet soils and also is cultivated as a garden plant for its flowers, which attract butterflies and other pollinators with nectar.

  • It belongs to the Apocynaceae family. iNaturalist
  • USDA PLANTS describes it as an herb (forb) with a perennial life cycle. USDA PLANTS
  • USDA PLANTS lists it as native in the lower 48 states and records it in 43 states. USDA PLANTS
  • In New York, most iNaturalist sightings of it in flower come in June–August. iNaturalist
  • In Ohio, most iNaturalist sightings of it in flower come in June–August. iNaturalist
  • USDA PLANTS lists its flower color as red. USDA PLANTS
  • USDA PLANTS gives its bloom period as fall. USDA PLANTS
  • USDA PLANTS lists a mature height of about 4.9 ft. USDA PLANTS
  • iNaturalist has 4,500 research-grade sightings of it in New York, ranking #49 among the 193 flowers on our New York list. iNaturalist
  • iNaturalist has 3,737 research-grade sightings of it in Ohio, ranking #41 among the 186 flowers on our Ohio list. iNaturalist
  • iNaturalist has 3,677 research-grade sightings of it in Michigan, ranking #28 among the 172 flowers on our Michigan list. iNaturalist

When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (4,583 records)
Bloom time in the 17 states whose Bloomipedia list includes it
StateTypePeak bloomSightings*
New YorkNativeJune–August4,500
OhioNativeJune–August3,737
MichiganNativeJune–August3,677
IllinoisNativeJune–August3,456
WisconsinNativeJuly–August3,269
MinnesotaNativeJune–August3,065
PennsylvaniaNativeJune–August2,354
MassachusettsNativeJuly–August1,781
MarylandNativeJune–August1,280
New JerseyNativeJune–August1,144
IndianaNativeJuly–August1,135
IowaNativeJuly–August695
NebraskaNativefew records (30)358
South DakotaNativefew records (9)302
New HampshireNativeJuly–August263
Rhode IslandNativeJuly–August235
DelawareNativefew records (30)162

Conservation status

Federal (U.S. ESA)
Not listed Not listed under the Endangered Species Act. USFWS ECOS does track it with the label “Not Listed,” which is informal and gives no legal protection. USFWS ECOS
NatureServe global
G5 Secure worldwide. NatureServe
State rare plant lists
Not listed Not on the official rare plant list in 15 of our 17 states.
See each state
New York
Not listed Not on New York protected native plants (6 NYCRR § 193.3). NatureServe: S5, secure in New York. 6 NYCRR § 193.3
Ohio
Not listed Not on Ohio endangered and threatened plants (Ohio Adm. Code 1501:18-1-03, eff. Dec. 26, 2024). NatureServe: SNR, not yet ranked in Ohio. OAC 1501:18-1-03
Michigan
Not listed Not on Michigan endangered and threatened plants (Mich. Admin. Code R 299.1028, eff. March 20, 2023). NatureServe: SNR, not yet ranked in Michigan. R 299.1028
Illinois
Not listed Not on Illinois List of Endangered and Threatened Flora (17 Ill. Adm. Code 1050), per the Endangered Species Protection Board's 2025 checklist. NatureServe: SNR, not yet ranked in Illinois. IL E&T checklist 2025
Wisconsin
Not listed Not on Wisconsin endangered and threatened species list (Wis. Admin. Code NR 27.03). NatureServe: SNR, not yet ranked in Wisconsin. NR 27.03
Minnesota
Not listed Not on Minnesota endangered, threatened and special concern plants (Minn. R. 6134.0300). NatureServe: SNR, not yet ranked in Minnesota. Minn. R. 6134.0300
Pennsylvania
Not listed Not on Pennsylvania classified native plants (17 Pa. Code Ch. 45, Subchapter B, as amended 2023). NatureServe: S5, secure in Pennsylvania. 17 Pa. Code Ch. 45
Massachusetts
Not listed Not on Massachusetts Endangered Species Act list (321 CMR 10.90). NatureServe: SNR, not yet ranked in Massachusetts. MESA list
Maryland
Not listed Not on Maryland threatened and endangered plants (COMAR 08.03.08.05, .06 and .08). NatureServe: SNR, not yet ranked in Maryland. COMAR 08.03.08
New Jersey
Not listed Not on New Jersey Endangered Plant Species List (N.J.A.C. 7:5C-5.1). NatureServe: SNR, not yet ranked in New Jersey. N.J.A.C. 7:5C-5.1
Iowa
Not listed Not on Iowa endangered, threatened and special concern plants (Iowa Admin. Code r. 571-77.3). NatureServe: S5, secure in Iowa. IAC 571-77.3
Nebraska
Not listed Not on Nebraska threatened and endangered species (163 Neb. Admin. Code ch. 4, § 004). NatureServe: SNR, not yet ranked in Nebraska. 163 NAC 4-004
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
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
Delaware
Not listed Not on Rare and Uncommon Plants of Delaware (DNREC, 2024; informational, Delaware has no state plant-protection list). NatureServe: S5, secure in Delaware. DE rare plants 2024
Indiana
No list Indiana has no state law listing endangered or threatened plants (the DNR keeps a rare plant list, but it isn't regulatory), so we show NatureServe's Indiana ranks instead. NatureServe: S5, secure in Indiana.
South Dakota
No list South Dakota's endangered and threatened list (ARSD 41:10:02) covers animals only, so we show NatureServe's South Dakota ranks for plants. NatureServe: SNR, not yet ranked in South Dakota.
Rare elsewhere
Other states where NatureServe ranks it rare or missing: AR (S2), AZ (S1), ID (S2), LA (S2), MS (S1), MT (S1), NV (S1), UT (S2), WY (S2). (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 peoplePoisonous to people

NC State Extension lists it as poisonous to humans (severity: low). Poisonous parts: flowers, fruits, leaves, roots, seeds, stems. Symptoms they list: “Can cause stomach upset, nausea, vomiting, abdominal pain, diarrhea, weakness, lethargy, and confusion if eaten in quantity. Milky sap can cause contact dermatitis and eye irritation” NC State Extension

For petsToxic to dogs, cats and horses

ASPCA's entry “Milkweed” (Asclepias species), which covers the whole genus, lists it as toxic to dogs, cats and horses. ASPCA

🌿 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 milkweed in 43 states plus Washington, D.C.

recorded by USDA PLANTS on our state lists not recorded

See the full list of states

Alabama, Arkansas, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, West Virginia, Wisconsin, Wyoming; District of Columbia.

New York counties with USDA records: Albany, Bronx, Broome, Cattaraugus, Chautauqua, Chenango, Clinton, Columbia, Delaware, Dutchess, Erie, Essex, Franklin, Greene, Herkimer, Jefferson, Kings, Lewis, Livingston, Madison, Monroe, Nassau, New York, Oneida, Onondaga, Ontario, Orange, Orleans, Oswego, Otsego, Putnam, Queens, Richmond, Rockland, Saratoga, Schenectady, Schuyler, St. Lawrence, Suffolk, Sullivan, Tompkins, Ulster, Warren, Washington, Westchester, Yates.

Ohio counties with USDA records: Adams, Ashland, Ashtabula, Athens, Auglaize, Belmont, Brown, Butler, Carroll, Champaign, Clark, Clermont, Clinton, Columbiana, Coshocton, Crawford, Cuyahoga, Darke, Defiance, Delaware, Erie, Fairfield, Fayette, Franklin, Fulton, Gallia, Geauga, Guernsey, Hamilton, Hancock, Hardin, Harrison, Henry, Highland, Hocking, Holmes, Huron, Jackson, Jefferson, Knox, Lake, Lawrence, Licking, Logan, Lorain, Lucas, Madison, Mahoning, Marion, Medina, Meigs, Mercer, Miami, Monroe, Montgomery, Morgan, Morrow, Muskingum, Noble, Ottawa, Paulding, Perry, Pickaway, Pike, Portage, Preble, Putnam, Richland, Ross, Sandusky, Scioto, Seneca, Shelby, Stark, Summit, Trumbull, Tuscarawas, Union, Van Wert, Vinton, Warren, Washington, Wayne, Williams, Wood, Wyandot.

Michigan counties with USDA records: Alcona, Allegan, Alpena, Antrim, Arenac, Baraga, Barry, Bay, Benzie, Berrien, Branch, Calhoun, Cass, Charlevoix, Cheboygan, Chippewa, Clare, Clinton, Crawford, Delta, Dickinson, Eaton, Emmet, Genesee, Gogebic, Grand Traverse, Gratiot, Hillsdale, Houghton, Huron, Ingham, Iosco, Isabella, Jackson, Kalamazoo, Kalkaska, Kent, Lake, Lapeer, Leelanau, Lenawee, Livingston, Luce, Mackinac, Macomb, Manistee, Marquette, Mason, Mecosta, Menominee, Midland, Missaukee, Monroe, Montcalm, Montmorency, Muskegon, Newaygo, Oakland, Oceana, Ogemaw, Ontonagon, Otsego, Ottawa, Presque Isle, Roscommon, Saginaw, Sanilac, Schoolcraft, Shiawassee, St. Clair, St. Joseph, Tuscola, Van Buren, Washtenaw, Wayne, Wexford.

Growing conditions

USDA PLANTS gives Swamp milkweed a high shade tolerance, none drought tolerance and high moisture use. It is rated for soil pH 5.0 to 8.0 and winter lows down to -38 °F.

Shade tolerance
High
Drought tolerance
None
Moisture use
High
Soil textures it is adapted to
medium, fine
Soil pH range
5.0 to 8.0
Minimum temperature tolerated
-38 °F
Frost-free days needed (minimum)
107
Annual precipitation range
15 to 65 inches
Minimum root depth
18 inches
Salinity tolerance
None
Fertility requirement
Medium
Growth rate
Moderate
Lifespan
Moderate
Active growth period
Spring
Fruit or seed
Brown · Spring to Fall
Can be propagated by
seed, sprigs
Commercial availability
Routinely Available

From the USDA PLANTS characteristics data for ASIN. 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 1356 counties across 41 states; the most are in Illinois (99), Virginia (95), Ohio (86).

Other Asclepias on Bloomipedia (16): Common milkweed, Butterfly milkweed, Green antelopehorns, Antelopehorn milkweed, Showy milkweed, Narrowleaf milkweed, Green comet milkweed, Zizotes milkweed, Tropical milkweed, Redring milkweed.

More from the Apocynaceae family (28 on Bloomipedia; most observed first): Lesser periwinkle, Greater periwinkle, Spreading dogbane, Pearl milkweed, Madagascar periwinkle, Honey-vine climbing milkweed, Hartweg's climbing milkweed, Oleander.

More New York flowers

Common milkweed (Asclepias syriaca)

Common milkweed

Asclepias syriaca

Native

🌼 Blooms in NY: June–July
Lesser periwinkle (Vinca minor)

Lesser periwinkle

Vinca minor

Introduced

🌼 Blooms in NY: March–May
Butterfly milkweed (Asclepias tuberosa)

Butterfly milkweed

Asclepias tuberosa

Native

🌼 Blooms in NY: June–August

Sources