(90-120 days. Hypericum perforatum) St John’s Wort plant is a short, woody shrub that grows about 24 inches tall and has fragrant yellow flowers from mid to late summer. Hypericum St John’s Wort was apparently named after John the Baptist, and historically has been used to ward off evil spirits and witches. As an herb plant, the oil in the leaves has been used topically for wounds, sunburns, and general aches and pains. St John’s Wort herb has also been used to treat mild depression and insomnia with some success. St. John’s Wort ground cover is often used to cover areas along side walks and driveways. The plants will tolerate most any soil conditions but prefer moist and light soils. Fertilizer is only necessary in the poorest of soils, and water only in times of prolonged drought.