St. John's wort is a plant with yellow, star-shaped flowers and five petals that grows in Europe, North and South America, Australia, New Zealand, and Eastern Asia. The plant grows in sunny, well-drained areas. It grows to be 50-100 cm tall.
St. John's wort is most commonly used for "the blues" or depression and symptoms that sometimes go along with mood such as nervousness, tiredness, poor appetite, and trouble sleeping. There is some strong scientific evidence that it is effective for mild to moderate depression.