Herb to Know: St. John’s Wort

• Hypericum perforatum
• Family Hypericaceae
• Hardy perennial

Some peopleswear 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.)

Other beliefs about the protective power of St.-John’s-wort persisted. For example, sleeping with a piece of the herb under the pillow on St. John’s Eve would ensure the saint’s blessing and protection from dying during the coming year. Welsh families predicted life expectancies by hanging a sprig for each member and noting the next day how shriveled the leaves were.

Medicinal Uses

The history of St.-John’s-wort as a medicinal herb has ancient roots. Another common name was amber touch-and-heal, and early English herbalists esteemed it as a treatment for deep sword cuts and other wounds. According to the “doctrine of signatures”, the oil glands in the leaves resembled pores in the skin, suggesting that the herb must be good for healing skin problems. The red oil extracted from the flowers by soaking them in olive or other vegetable oil was used externally to treat burns, neuralgia, hard tumors, caked breasts, bruises, and sciatica.

The herb has been taken internally to treat cancer, rabies, gout, arthritis, respiratory and gastrointestinal ailments, menstrual cramps, and nervous disorders. Reputed to be a diuretic, it also has been and continues to be prescribed to cure bedwetting.

American Indians used H. perforatum and other hypericums to treat a wide range of ills. For example, the Cherokee used H. perforatum to reduce fever, promote menstruation, and treat diarrhea, nosebleed, venereal disease, and snakebite; they washed their babies with an infusion of the roots to make them strong. The Fox and Menominee used the related H. ascyron in a tuberculosis remedy.

Present-day herbalists consider St.-John’s-wort a relaxing restorative and prescribe it for insomnia, depression, and unpleasant symptoms associated with menopause. The oil is applied externally to relieve the pain of neuralgia and promote the healing of burns, bruises, and hemorrhoids, and is taken internally for intestinal disorders.

A number of studies in the past decade have suggested that St.-John’s-wort has some antidepressant effect. Extracts of St.-John’s-wort have been shown to inhibit the growth of the bacterium that causes tuberculosis. Other studies have confirmed anti-inflammatory, antiseptic, and antispasmodic activity. The hopes that St.-John’s-wort might be a cure for cancer and a treatment of aids apparently have not been fulfilled. The principal active constituent is hypericin, the red pigment in the oil.

Despite its long history and current use in Europe as a healing herb, St.-John’s-wort has been judged unsafe by the U.S. Food and Drug Administration. When the herb is taken internally, the hypericin can sensitize nerve endings to sunlight, causing dermatitis when the skin is subsequently exposed to the sun. In some individuals, this photosensitivity can be activated merely by touching the plant, as it can with rue.

Other Uses

St.-John’s-wort doesn’t hold a prominent place in the kitchen, except perhaps in arrangements of cut flowers. The tops can be made into a beverage tea that is somewhat bitter and astringent, and the flowers have been used to flavor mead (a fermented beverage that contains honey) and vermouth.

The red pigment has been used as a dyestuff for silk and wool. The flowers yield a deep violet-red dye. Using a tin mordant produces an orange-red, and an alum mordant gives yellow. The stems yield a brown dye with alum.

Growing It

St. John’s wort is hardy to USDA Zone 3 and also grows well in the South. It thrives in poor to average soil and is not particular as to soil pH. Plant it in full sun or part shade. Seeds germinate best if not covered; just press them into moist soil. Plants will spread of their own accord, or you can increase them faster by rooting stem cuttings or taking root divisions.

Not Growing It

In some parts of the world, ranchers would just as soon St.-John’s-wort didn’t increase at all. The same photosensitivity reaction following ingestion of St.-John’s-wort mentioned above has killed or injured millions of grazing animals, particularly light-colored ones, in the western United States, Canada, Australia, and New Zealand. St.-John’s-wort is thus considered “one of the most toxic pasture weeds in New Zealand”. (In the West, it is known as Klamath weed because it appeared in California near the Klamath River about 1900.) It aggressively takes over rangelands, especially those that have been overgrazed.

Even though animals do not relish the herb, they eat it if they are hungry enough. Shedding of the wool or hair, swelling of the face, loss of appetite, blindness, and death from starvation may follow. Efforts to eliminate St.-John’s-wort have included plowing it under, repeated mowing, and herbicides, but the only effective control has been the introduction of two European species of beetle whose only food plant is H. perforatum. While the beetles seem to keep the plants in check, they don’t keep the species from spreading to new areas and driving out native species. In Colorado, St.-John’s-wort grew for years in one restricted site, nibbled on by one of the species of beetle, but recently plants have been discovered elsewhere in the state, and St.-John’s-wort now shows signs of becoming a major pest.


• The Flowery Branch, PO Box 1330, Flowery Branch, GA 30542. Catalog $2. Seeds of this and six other species.
• The Thyme Garden, 20546 Alsea Hwy., Alsea, OR 97324. Catalog $1.50, refundable. Seeds.
• Well-Sweep Herb Farm, 317 Mt. Bethel Rd., Port Murray, NJ 07865. Catalog $2. Plants.

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