Plants annual or perennial, shrubs or herbs. Leaves without stipules. usually opposite, rarely whorled; blades simple, usually entire, rarely glandular-fringed, with translucent oil-containing glands, sometimes also with black or reddish glands. Flowers radiallt symmetric, bisexual, hypogynous; sepals 4-5, free or partly united, sometimes glandular, overlapping in bud; petals 4-5, yellow, often tinged with red, usually with glands, twisted in bud; stamens many, in fascicles opposite the petals, or all united, or all free; ovaries superior, 1-5-celled, with 2-5 axile placentas. Fruits usually capsules, occasionally berries; seeds cylindric, small.
Hypericum has about 400 species. They grow in temperate regions and at high elevations in tropical mountains. They contain many compounds of pharmacological interest; some are beneficial others are not. Hypericin, the compound found in the reddish or black glands, can make animals photosensitive if eaten in sufficient quantity. Animals will voluntarily avoid eating Hypericum if there are other palatable plants around.