common St. Johnswort USDA PLANTS SYMBOL: HYPE
Hypericum perforatum L.
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.

Identification, Biology, Control and Management Resources