common St. Johnswort

Hypericum perforatum L.

Description from Invasive.org

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.

Resources


Selected Images from Invasive.org

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Flower(s)
Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org
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Feature(s) pellucid dots
Ohio State Weed Lab , The Ohio State University, Bugwood.org
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Fruit(s)
Steve Dewey, Utah State University, Bugwood.org
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Flower(s)
David Cappaert, , Bugwood.org
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Flower(s)
Jamie Nielsen, University of Alaska Fairbanks, Cooperative Extension Service, Bugwood.org
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Flower(s)
Steve Dewey, Utah State University, Bugwood.org
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Plant(s) Mature plant
Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org
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Infestation research site near
Norman E. Rees, USDA Agricultural Research Service - Retired, Bugwood.org
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Flower(s)
Steve Dewey, Utah State University, Bugwood.org
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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
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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 NRCS PLANTS Database , USDA NRCS PLANTS Database, Bugwood.org
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Seed(s)
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
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Distribution