This perennial member of the St. John’s-wort family is, in many ways, an unusual plant. Most other St. Johns-wort species have a yellow flower with 5 petals and numerous stamens. This species produces a flower that is pale pink or cream in color. They grow on top of the plant and from the leaf axils. Each flower has 9-12 yellow-tipped stamens and 5 petals. Green sepals surround the base of the flower. This flower lasts such a short time that it is seldom seen. Instead it is the fruit that is most commonly seen, taking the form of bright red or maroon, three-sectioned capsules. These capsules are pointed at the tip and are often mistaken for buds.

The blooming period for this plant is in July or August. The species grows throughout eastern and central Canada and the United States. The leaves are oval to egg-shaped or rounded. There is no leaf stalk and the larger leaves often clasp the stem. The stem and at least the upper leaves are often red or reddish tinted. As its common name indicates, this is a wetland plant, growing in sunny or partly sunny areas along shorelines of bogs, marshes, fens and ponds. It grows 1-2 feet tall.

This species is also called bog St. Johnswort, Frasier’s marsh St. Johnswort or Virginia marsh St. Johnswort. The multiple scientific names reflect recent reclassification of the species. The genus name Tridenum comes form the 3 glands found inside the flower. The other St. Johnswort species belong to the genus Hypericum.