Perforate St John's-wort (Common Saint John's wort, St John's wort)
Hypericum perforatum, known as Perforate St John's-wort, Common Saint John's wort and St John's wort,[note 1] is a flowering plant in the family Hypericaceae. The common name "St John's wort" may be used to refer to any species of the genus Hypericum. Therefore, Hypericum perforatum is sometimes called "Common St John's wort" or "Perforate St John's wort" in order to differentiate it. It is a medicinal herb with antidepressant activity and potent anti-inflammatory properties as an arachidonate 5-lipoxygenase inhibitor and COX-1 inhibitor.
Hypericum perforatum is native to parts of Europe and Asia, but has spread worldwide as a cosmopolitan invasive weed, including to temperate regions of India, China, Canada, Africa, and the United States.
The common name "St John's wort" comes from its traditional flowering and harvesting on St John's day, 24 June. The genus name Hypericum is derived from the Greek words hyper (above) and eikon (picture), in reference to the tradition of hanging plants over religious icons in the home during St John's day, to ward off evil.
Perforate St John's wort is a herbaceous perennial plant with extensive, creeping rhizomes. Its stems are erect, branched in the upper section, and can grow to 1 m high. It has opposite, stalkless, narrow, oblong leaves that are 1–2 cm long. The leaves are yellow-green in color, with scattered translucent dots of glandular tissue. The dots are conspicuous when held up to the light, giving the leaves the 'perforated' appearance to which the plant's Latin name refers. The flowers measure up to 2.5 cm across, have five petals, and are colored bright yellow with conspicuous black dots. The flowers appear in broad cymes at the ends of the upper branches, between late spring and early to mid summer. The sepals are pointed, with black glandular dots. There are many stamens, which are united at the base into three bundles. The pollen grains are ellipsoidal.
When flower buds (not the flowers themselves) or seed pods are crushed, a reddish/purple liquid is produced.