| common St. Johnswort |
USDA PLANTS Symbol: HYPE USDA ARS GRIN: 19600 ITIS: 21454 NAPIS: PCBABBA |
| Hypericum perforatum L. | |
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Taxonomic Rank: Magnoliopsida: Theales: Clusiaceae |
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| Synonym(s): Klamathweed, St. John's wort | |
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
- Fire Effects Information System - USDA Forest Service
| Selected Images from Invasive.org | View All Images at Invasive.org |
 Plant(s); Richard Old, XID Services, Inc., Bugwood.org Additional Resolutions & Image Usage |
 Feature(s); pellucid dots on leaves Richard Old, XID Services, Inc., Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Richard Old, XID Services, Inc., Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Norman E. Rees, USDA Agricultural Research Service, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); David Cappaert, Michigan State University, Bugwood.org Additional Resolutions & Image Usage |
 Flower(s); Steve Dewey, Utah 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 |
 Feature(s); Roots Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Fruit(s); Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Mature plant Norman E. Rees, USDA Agricultural Research Service, 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 |
 Infestation; research site near Norman E. Rees, USDA Agricultural Research Service, Bugwood.org Additional Resolutions & Image Usage |
 Seed(s); Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage |
 Diagram or Graphic; 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 |
Taxonomic References:
- USDA, NRCS. 2001. The PLANTS Database, Version 3.1, National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Invasive Listing Sources:
- City of Ann Arbor Michigan Parks and Recreation
- Faith Campbell, 1998. Plants that Hog the Garden: Invasive Plants in the United States. Fine Gardening Online
- Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
- Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
- John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
- Missouri Department of Conservation,
- Native Plant Society of Oregon, 2002
- Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
- Pacific Northwest Exotic Pest Plant Council, 1998
- WeedUS - Database of Plants Invading Natural Areas in the United States
- California Invasive Plant Council
- California Noxious Weeds
- Colorado Noxious Weeds
- Kentucky Exotic Pest Plant Council Lesser Threat
- Montana Noxious Weeds
- Nevada Noxious Weeds
- Oregon Noxious Weeds
- South Dakota Noxious Weeds
- Tennessee Exotic Pest Plant Council Watch List A
- Washington Noxious Weeds
- Wyoming Noxious Weeds
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