Hypericum perforatum L.
Family: Hypericaceae
common St. John's-wort, Klamath-weed, St. John's-wort
Hypericum perforatum image
Christopher Noll  
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Merel R. Black  
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University of Wisconsin - Madison (WIS-VP)  
Etymology: Hypericum: ancient Greek name derived from hyper, "above," and eikon, "picture," from old practice of placing flowers above an image in the house to ward off evil spirits at the midsummer festival of Walpurgisnacht, which later became feast of St. John
Plants: erect, perennial, 2'-3' tall forb with many leafy branches; stems with a sharp ridge below the base of the leaves
Leaves: stalkless, small, 1/4" wide leaf drawing
Flowers: yellow, 5-parted, 5/8"-1" wide, stalked, petals with black dots near the edges; inflorescence a many-flowered, rounded to flat, compound, branched cluster (cyme); blooms June-Sept.
Fruits: 3 chambered capsule fruit drawing
Habitat: disturbed sites, fields, roadsides
Hazardous: Careful, this plant is hazardous!
Invasiveness: Invasive - Eradicate!
Conservation Status: Introduced - naturalized; ecologically invasive
Fields, thickets, along roadsides and railroads, dry to mesic prairies, dumps, old quarries, oak barrens, along trails and logging roads, beaches and lake dunes, sand and gravel pits, clay bluffs, rock outcrops, blufftops, lakeshores, thin woods of oak or pine, open sandy areas. Our only species introduced from Europe, first collected in 1860. Contact of the sap with exposed skin can cause photodermatitis in some people.
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Merel R. Black  
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Michael Clayton  
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Merel R. Black  
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Emmet J. Judziewicz  
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Merel R. Black  
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Margery Melgaard  
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Damon A. Smith  
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Botanical Illustration  
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Botanical Illustration  
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Botanical Illustration  
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Botanical Illustration  
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Aaron_Carlson  
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Aaron_Carlson  
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Aaron_Carlson  
Hypericum perforatum image
Hypericum perforatum image
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Aaron_Carlson  
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Aaron_Carlson