Flower profile

Common St. John's wort

Hypericum perforatum

Introduced in the lower 48

Common St. John's wort is a wildflower that USDA PLANTS lists as introduced in the lower 48 states. It's on our flower lists for 6 states, and across the U.S. it's most often seen in bloom in June–September.

45states

6of our state lists

22,337U.S. sightings*

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

On our lists for: Massachusetts, Michigan, New Hampshire, Oregon, Rhode Island, Washington

🚫

Regulated invasive plant in Washington and Oregon. It's on those states' official invasive plant lists (Washington: Class C noxious weed; Oregon: "B" noxious weed (sale and transport prohibited)). Please don't plant or share it there. ^{WAC 16-750 OAR 603-052-1200}

Quick look

Hypericum perforatum, commonly known as St. John's wort, is a flowering plant in the family Hypericaceae. It is a hairless, perennial herb with woody roots, yellow flowers marked by black glands, and leaves that appear perforated due to translucent glands, producing thousands of seeds per plant.
From Wikipedia's article Hypericum perforatum, CC BY-SA 4.0.

It belongs to the Hypericaceae family. ^iNaturalist
USDA PLANTS describes it as an herb (forb) with a perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as introduced in the lower 48 states and records it in 45 states. ^{USDA PLANTS}
NatureServe lists it as not native to Washington, Oregon, Michigan, Massachusetts, New Hampshire and Rhode Island. ^NatureServe
In Washington, most iNaturalist sightings of it in flower come in June–September. ^iNaturalist
In Oregon, most iNaturalist sightings of it in flower come in June–September. ^iNaturalist
iNaturalist has 2,985 research-grade sightings of it in Washington, ranking #58 among the 110 flowers on our Washington list. ^iNaturalist
iNaturalist has 2,280 research-grade sightings of it in Oregon, ranking #72 among the 110 flowers on our Oregon list. ^iNaturalist
iNaturalist has 1,627 research-grade sightings of it in Michigan, ranking #101 among the 111 flowers on our Michigan list. ^iNaturalist

State flower gift ideas

This one is a regulated invasive plant, so here are state flower gifts instead.

🌱 Sample spot. Handmade gift picks from independent shops will appear here once our shop partnership is approved. These cards are placeholders, not real products.

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State flower print
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Birth-flower necklace
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Wildflower seed favors
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Botanical tea towel
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Pressed-flower frame
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Flower-garden mug
Gift pick coming soon

When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (3,002 records)

Bloom time in each of our 6 states

State	Type	Peak bloom	Sightings*
Washington	Introduced	June–September	2,985
Oregon	Introduced	June–September	2,280
Michigan	Introduced	June–September	1,627
Massachusetts	Introduced	June–August	1,459
New Hampshire	Introduced	June–August	445
Rhode Island	Introduced	June–July	222

Conservation status

Federal (U.S. ESA): Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. ^{USFWS ECOS}
NatureServe global: GNR Not yet ranked worldwide. ^NatureServe
Washington: No list Washington has no state law listing endangered or threatened plants (the Washington Natural Heritage Program's rare plant list isn't regulatory), so we show NatureServe's Washington ranks instead. NatureServe: SNA, not applicable (usually because it isn't native there) in Washington.
Oregon: Not listed Not on Oregon endangered and threatened plants (OAR 603-073-0070). NatureServe: SNA, not applicable (usually because it isn't native there) in Oregon. ^{OAR 603-073-0070}
Michigan: Not listed Not on Michigan endangered and threatened plants (Mich. Admin. Code R 299.1028, eff. March 20, 2023). NatureServe: SNA, not applicable (usually because it isn't native there) in Michigan. ^{R 299.1028}
Massachusetts: Not listed Not on Massachusetts Endangered Species Act list (321 CMR 10.90). NatureServe: SNA, not applicable (usually because it isn't native there) in Massachusetts. ^{MESA list}
New Hampshire: Not listed Not on New Hampshire Official Rare Plants List (Ncr 312, eff. Jan 1, 2020). NatureServe: SNA, not applicable (usually because it isn't native there) 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: SNA, not applicable (usually because it isn't native there) in Rhode Island. ^{RI rare plants 2016}
Rare elsewhere: No other U.S. state ranks it S1, S2, SH or SX.

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

Can you eat it?

For peopleCaution: partly edible, partly poisonous

NC State Extension lists it as poisonous to humans (severity: medium). Poisonous parts: leaves, sap/juice. Symptoms they list: “Skin contact with the sap, or ingestion of the plant, can cause photosensitivity in some people. Common side-effects are gastointestinal disturbances, allergic reactions and fatigue, ulcerative and exudative dermatitis.” They also note: “Ingestion of St John's wort can reduce the effectiveness of prescription medicine.” ^{NC State Extension}

For petsToxic to dogs, cats and horses

ASPCA's entry “Klamath Weed” (Hypericum perforatum) 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 common St. John's wort in 45 states plus Washington, D.C.

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recorded by USDA PLANTS on our state lists not recorded

See the full list of states

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

Washington counties with USDA records: Adams, Asotin, Benton, Chelan, Clallam, Clark, Columbia, Cowlitz, Douglas, Ferry, Franklin, Garfield, Grant, Grays Harbor, Island, King, Kitsap, Kittitas, Klickitat, Lewis, Lincoln, Okanogan, Pacific, Pend Oreille, Pierce, San Juan, Skagit, Skamania, Snohomish, Spokane, Stevens, Thurston, Wahkiakum, Walla Walla, Whatcom, Whitman, Yakima.

Oregon counties with USDA records: Benton, Clackamas, Clatsop, Columbia, Coos, Crook, Curry, Deschutes, Douglas, Gilliam, Grant, Harney, Hood River, Jackson, Jefferson, Josephine, Klamath, Lake, Lane, Lincoln, Linn, Marion, Multnomah, Polk, Sherman, Tillamook, Umatilla, Union, Wallowa, Wasco, Washington, Wheeler, Yamhill.

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

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Sources

USDA, NRCS. PLANTS Database, profile HYPE.
iNaturalist, Hypericum perforatum: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
Wikipedia, Hypericum perforatum (lead quoted under CC BY-SA 4.0).
Washington: Washington State noxious weed list (WAC 16-750-005, -011, -015).
Oregon: Oregon endangered and threatened plants (OAR 603-073-0070).
Oregon: Oregon noxious weed quarantine, A and B weeds (OAR 603-052-1200).
Michigan: Michigan endangered and threatened plants (Mich. Admin. Code R 299.1028, eff. March 20, 2023).
Michigan: Michigan prohibited and restricted species (NREPA Part 413 and the 2026 Invasive Species Order), as listed by Michigan's Invasive Species Program.
Massachusetts: Massachusetts Endangered Species Act list (321 CMR 10.90).
Massachusetts: Massachusetts Prohibited Plant List (MDAR) (Text from MDAR's 2023 scientific-name PDF (mass.gov blocks automated downloads); 2024-2026 additions listed on the mass.gov page: Alnus glutinosa, Pyrus calleryana, Miscanthus sinensis, Aralia elata, Rhodotypos scandens, Symplocos paniculata.).
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).
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, Hypericum perforatum (global and state ranks).
Edibility and toxicity: NC State Extension; ASPCA.
Photo: Laura J. Costello via iNaturalist · CC BY 4.0 · resized.