Hypericum perforatum is only one of a number of herbs of Saint John once employed as amulets at midsummer. The botanical name of the genus preserves its ancient use as a fuga daemonum, or devil chaser. The Latin Hypericum comes from the Greek hyper eikon; some authorities interpret this as “over an apparition,” in reference to the plant’s use against supernatural agents (Grieve, A Modern Herbal, 1931), while others derive it from the practice of placing a sprig of St. John’s wort above an icon in the house for protective purposes. The first-century herbalist Dioscorides, in his De Materia Medica, refers to several related species by the term Hyperikon; these are unmistakably of the genus we know as Hypericum, and include H. perforatum. Thus the first and older of the two explanations would seem to hold, although the second practice may have derived from the first. (Dioscorides discusses only the medicinal and not the magical aspects of the plant.)
The sign of the plant’s special association with the saint is in the yellow flowers that bloom at the solstice. When crushed, the flower buds yield a watery, purplish-red liquid, associated with the blood of the beheaded Saint John the Baptist, whose birth was celebrated on June 24. (The feast of his decollation—i.e., decapitation—at Herod’s command was celebrated on August 29). While St. John’s wort warded off witches and ill fortune at midsummer, it was employed as a medicinal herb at other times; the Hortus Sanitatis recommends its use to stanch bleeding, bind wounds, join cut sinews, and counteract the thrusts of poisoned weapons (Anderson, German Herbals Through 1500, 1984). Still in use as a folk remedy, the crushed blossoms of the plant, when steeped in oil, turn the oil blood red; the oil is then used to treat wounds.
Widely naturalized in meadows in the U.S., St. John’s wort is considered a noxious weed in some states.