Herb to Know: St. John's Wort

Get to know this sometimes controversial herb.

• Hypericum perforatum 
• Family Hypericaceae
• Hardy perennial

Some people swear by it and others swear at it. In its native Europe, St.-John’s-wort is not a cause for complaint, but elsewhere its rampant habits and toxicity have made it planta non grata.

The genus Hypericum (which is variously assigned to the families Hypericaceae, Guttiferae, or Clusiaceae) contains some 300 species of plants ranging from creeping forms to 15-foot-tall shrubs. The species most familiar to herb gardeners is H. perforatum, found along roadsides and in fields and waste sites throughout much of North America and elsewhere. It is an erect, branching plant, growing 1 to 21/2 feet tall. The stems, which may be woody at the base, bear two lengthwise ridges and are sparsely clothed with pairs of 1-inch-long narrow leaves. These leaves are dotted with translucent oil glands that look like perforations, giving rise to the species name, perforatum. The ends of the stems bear showy, rounded or flat-topped clusters of 1-inch-wide bright yellow flowers. The five petals are often bordered with tiny black dots and yield a reddish resinous sap when crushed. The most striking feature of this and other hypericums is the bushy clump of stamens that bursts from the center of the flower. Bees visit them for their abundant pollen, but the flowers produce no nectar, and the seeds develop without fertilization. The fruit is a three-celled capsule that opens to reveal small, shiny black resinous seeds. An alternate common name is rosin rose. All parts of the plant smell like turpentine.

Many species of Hypericum are more ornamental, with a neater habit and showier flowers, than H. perforatum. One that is available in many nurseries is creeping St.-John’s-wort (H. calycinum), a shrubby form with larger leaves and 2-inch bright yellow flowers that is often grown as a ground cover.


Legends about St.-John’s-wort go back to antiquity. It was thought to ward off witches and annoying fairies as well as to protect one from thunder. Some believe that the generic name, Hypericum, is derived from the Greek words hyper (“above”) and eikon (“image”), referring to the custom of hanging a sprig above a picture to repel evil spirits; others hold that Hypericum means “above an apparition” and refers to the power of the odor to banish spirits. A more prosaic theory is that Hypericum comes from Greek words meaning “above (or below) the heather” and refers (maybe) to where the plants grow or to their relative height.

Early Christians adopted the herb as a symbol of St. John the Baptist, perhaps because it flowered on June 24, when his birth was celebrated. Some also observed that the leaves “bled” red oil on August 29, the anniversary of his beheading. (These dates may have been adjusted with the later adoption of the Gregorian calendar, but the observations still apply as plants bloom from June through September, and the leaves exude oil on crushing throughout the growing season.)

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