St John's wort is the plant species Hypericum perforatum, also known as Tipton's Weed or Klamath weed, but, with qualifiers, is used to refer to any species of the genus Hypericum. Therefore, H. perforatum is sometimes called Common St John's wort to differentiate it. The species of Hypericum have been placed by some in the family Hypericaceae, but more recently have been included in the Clusiaceae.[2] Approximately 370 species of the genus Hypericum exist worldwide with a native geographical distribution including temperate and subtropical regions of North America, Europe, Asia Minor, Russia, India, and China.