Creeping St. John's Wort

Description:

St. John's-worts vary from annual or perennial herbaceous herbs 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. The fruit is usually a dry capsule which splits to release the numerous small seeds; in some species it is fleshy and berry-like.

Habitat:

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, though they are also commonly just called hypericum, and some are known as tutsan. The marsh St. John's-worts are nowadays separated into the genus Triadenum.

Notes:

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 Hypericum × moserianum (H. calycinum × H. patulum) and Hypericum calycinum cv. 'Hidcote'. St. John's-worts can occur as nuisance weeds in farmland and gardens. On pastures, some can be more than a nuisance, causing debilitating photosensitivity and sometimes abortion in livestock. The beetles Chrysolina quadrigemina, Chrysolina hyperici and the St. John's-wort Root Borer (Agrilus hyperici) like to feed on Common St. John's-wort (H. perforatum) and have been used for biocontrol where the plant has become an invasive weed. Hypericum species are the only known food plants of the caterpillar of the Treble-bar, a species of moth. Other Lepidoptera species whose larvae sometimes feed on Hypericum include Common Emerald, The Engrailed (recorded on Imperforate St. John's-wort, H. maculatum), Grey Pug and Setaceous Hebrew Character.