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
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.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView 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
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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
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.

U.S. National Parks where reported invasive:
Glacier National Park (Montana)
Yellowstone National Park (Wyoming)



Invasive Listing Sources:
California Invasive Plant Council
City of Ann Arbor Michigan Parks and Recreation
Faith Campbell, 1998
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.
Kentucky Exotic Pest Plant Council
Missouri Department of Conservation,
Native Plant Society of Oregon, 2008
Pacific Northwest Exotic Pest Plant Council, 1998
Tennessee Exotic Pest Plant Council