common St. Johnswort: Hypericum perforatum (Malpighiales: Hypericaceae): Invasive Plant Atlas of the United States

common St. Johnswort	USDA PLANTS Symbol: HYPE U.S. Nativity: Exotic Habit: Forbs/Herbs
Hypericum perforatum L.

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Taxonomic Rank: Magnoliopsida: Malpighiales: Hypericaceae
Synonym(s): Klamathweed, St. John's wort
Native Range: Europe (BAIL);
Appearance Hypericum perforatum is a perennial, rhizomatous herb that can reach 4 ft. (1.2 m) in height. Foliage Leaves are opposite, sessile, elliptic, 0.4-1.2 in. (1-3 cm) long and dotted with many pellucid glands. Flowers 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. Fruit The fruits are three-chambered capsules with three persistent styles. Ecological Threat Hypericum perforatum has been used to treat mild depression, but has been shown to cause hyper photosensitivity. Plants inhabit rangelands, pastures, roadsides and forest clearings. St Johnswort is native to Europe. Hypericum perforatum may be poisonous to cattle in large doses.

Identification, Biology, Control and Management Resources

Fire Effects Information System - USDA Forest Service

Selected Images from Invasive.org

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Flower(s); Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Jamie Nielsen, University of Alaska Fairbanks, Cooperative Extension Service, 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
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	Foliage; Steve Dewey, Utah State University, Bugwood.org Additional Resolutions & Image Usage	Seed(s); Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage
Plant(s); plant Eric Coombs, Oregon Department of Agriculture, Bugwood.org Additional Resolutions & Image Usage	Flower(s); Hypericum perforatum (common St. John's wort); note black spots restricted mostly to petal margins Rob Routledge, Sault College, Bugwood.org Additional Resolutions & Image Usage	Seedling(s); Joseph M. DiTomaso, University of California - Davis, 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