St. John’s Wort is a plant which tends to grow mainly in Europe. It is cultivated but often grows wild in fields and meadows where it can make quite a nuisance of itself as it is a toxic weed, not only killing other plants but also poisoning livestock. The first use of the plant for medicinal purposes was in ancient Greece. It was used by Native Americans as an antiseptic and has been used as a herbal tea for a long time.