I like St. John's Wort (Hyperieum). The shrubby herb grows throughout Britain, Europe, Asia, and in our garden, pictured below. The plant easily reaches three to four feet here, but may not get this tall elsewhere. The bright flowers are a cheery yellow most of the summer, followed by small round blackish seeds which have a resinous smell, said to taste bitter but I don't eat them.
There are many ancient superstitions regarding this herb. Its name Hyperieum comes from the Greek and means 'over an apparition,' a reference to the belief that the herb was so obnoxious to evil spirits that a whiff of it would cause them to fly.
"From the time of the ancient Greeks down through the Middle Ages, the plant was considered to be imbued with magical powers and was used to ward off evil and protect against disease."
Medicinal Action and Uses: Aromatic, astringent, resolvent, expectorant and nervine. Used in all pulmonary complaints, bladder troubles, in suppression of urine, dysentery, worms, diarrhea, hysteria and nervous depression, haemoptysis and other haemorrhages and jaundice. For children troubled with incontinence of urine at night an infusion or tea given before retiring will be found effectual; it is also useful in pulmonary consumption, chronic catarrh of the lungs, bowels or urinary passages. Externally for fomentations to dispel hard tumours, caked breasts, ecchymosis, etc.
Preparations and Dosages: 1 OZ. of the herb should be infused in a pint of water and 1 to 2 tablespoonsful taken as a dose. Fluid extract, 1/2 to 1 drachm.
The oil of St. John's Wort is made from the flowers infused in olive oil.
About St. John's Wort from the Mayo Clinic: http://www.mayoclinic.org/drugs-supplements/st-johns-wort/safety/HRB-20060053