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St. Johnswort (Hypericum)

Description

Hypericum is a genus of flowering plants in the family Hypericaceae (formerly considered a subfamily of Clusiaceae). Hypericum is unusual for a genus of its size because a worldwide taxonomic monograph was produced for it by Norman Robson (working at the Natural History Museum, London). Robson recognizes 36 sections within Hypericum. The genus has a nearly worldwide distribution, missing only from tropical lowlands, deserts and polar regions. All members of the genus may be referred to as St. John's wort, and some are known as tutsan. The white or pink flowered marsh St. John's-worts of North American and eastern Asia are now separated into the genus Triadenum. There are 490 individual species in the genus. Hypericums vary from herbaceous annual or perennials 5-10 cm tall to shrubs and small trees up to 12 m tall. The leaves are opposite, simple oval, 1-8 cm long, either deciduous or evergreen. The flowers vary from pale to dark yellow, and from 0.5-6 cm in diameter, with five (rarely four) petals, most having prominent stamens. The fruit is usually a dry capsule which splits to release the numerous small seeds. Some species are used as ornamental plants and have large, showy flowers. Numerous hybrids and cultivars have been developed for use in horticulture, such as H. - moserianum (H. calycinum - H. patulum), H. 'Hidcote' and H. 'Rowallane'. All of the above cultivars have gained the Royal Horticultural Society's Award of Garden Merit.

Taxonomic tree

  • Domain: Eukarya

    • Kingdom: Plantae

      • Phylum: Magnoliophyta

        • Class: Magnoliopsida

          • Order: Theales

            • Family: Clusiaceae

              • Genus: Hypericum