| common St. Johnswort | USDA PLANTS Symbol: HYPE U.S. Nativity: Exotic Habit: Forbs/Herbs |
| Hypericum perforatum L. |
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Taxonomic Rank: Magnoliopsida: Theales: Clusiaceae |
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| Synonym(s): Klamathweed, St. John's wort | |
| Native Range: Europe (BAIL); | |
Common St. Johnswort is a perennial, rhizomatous herb that can reach 4 ft (1.2 m) in height. Leaves are opposite, sessile, elliptic, 2/5- 1 1/5 in. (1-3 cm) long and dotted with many pellucid glands. Flowering occurs from June to September, when bright yellow flowers develop at the tips of the stems. Flowers have five petals and many stamens. Petals typically have black glands along the margins. Fruits are three-chambered capsules with three persistent styles. Plants have been used to treat mild depression, but have been shown to cause hyper photosensitivity. St Johnswort is native to Europe and may be poisonous to cattle in large doses. Plants inhabit rangelands, pastures, roadsides and forest clearings. |
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Identification, Biology, Control and Management Resources
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| Selected Images from Invasive.org | View All Images at Invasive.org |
 Flower(s); Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org Additional Resolutions & Image Usage |
 Feature(s); pellucid dots Ohio State Weed Lab Archive, The Ohio State University, Bugwood.org Additional Resolutions & Image Usage |
 Fruit(s); Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); David Cappaert, Michigan State University, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Jamie Nielsen, University of Alaska Fairbanks, Cooperative Extension Service, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Mature plant Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org Additional Resolutions & Image Usage |
 Infestation; research site near Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); St. John's Wort, native to Eurasia, is a serious problem in parts of the West where it displaces native plants that are important in maintaining soil nutrients, microbial activity, and water cycling. Carol DiSalvo, USDI National Park Service, Bugwood.org Additional Resolutions & Image Usage |
 Root(s); Roots Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 2: 533. USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage |
 Seed(s); Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage |
| EDDMapS Distribution: This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org Alternative content
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 State(s) Where Reported invasive. Based on state level agency and organization lists of invasive plants from WeedUS database. Alternative content
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| U.S. National Parks where reported invasive: |
| Glacier National Park (Montana) Yellowstone National Park (Wyoming) |
