Common St. Johnswort (Hypericum perforatum)


The Common St. Johnswort (Hypericum perforatum) is an herb in the Mangosteen Family (Clusiaceae) and order Theales. This common name derives from the tendency of this plant to bloom on St. John's Eve, June 24. Some authorities place this plant in the St. Johnswort Family (Hypericaceae). Other common names for this species are Klamath Weed,  St. John's Wort, Common St. John's Wort, Tipton's Weed and Chase-devil. This plant can grow to about 2½ feet (75 centimeters).

Each flower is yellow with five petals each of which have distinctive, black dots on the margins as shown in the photograph below. The numerous stamens are in the center of the flower in three groups. There are three styles. Beneath each flower are five, small, green speals. It flowers from June to September.

The leaves are elliptical, up to two inches (5 centimeters) long and arranged opposite along the stem. Each leaf has distinctive translucent dots.

The fruit is a ovoid, brown capsule containing reddish-brown seeds.

The root system is rhizomic.

Other plants may resemble Common St. Johnswort (Hypericum perforatum) but the black dots on the flower petals and translucent dots on the leaves are unique to the Common St. Johnswort.

This plant has medicinal uses, particularly to treat depression. However, it is toxic to livestock in large quantities. It helps stabilize soil and filter water. 

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