St John’s-wort (Hypericum perforatum) is a versatile plant that has been used for medicinal purposes in many ways. When you grind its flowers in your hand, it turns your fingers blood-red, and people used to believe that this colour was the blood of the beheaded John the Baptist or the blood of Christ from Golgotha.
The plant was used to treat several ailments as early on as in ancient Greece, most often on burns or for depression. St John’s-wort was originally a plant of rocky areas, and it has since then spread to railway embankments and fortresses of military islands.