This was on a placard in a garden adjacent to the Musée de Cluny in Paris:
The Book of Medicinal Simples, attributed to 12th century physician, Platearius, is one of the main sources of medicinal medicine. Early in the 15th century it was adopted as a codex by the Parisian apothecaries. The expression “medicinal simples” designates “simple” remedies, i.e. those made from a single plant, as opposed to compound drugs.
The Middle Ages made extensive use of plants because of their real or imaginary therapeutic virtues, often linked to their name or shape. Thus, Salvia officinalis, reigned in every pleasure and kitchen garden because of the etymology of its Latin name, which means “the healing plant.” The “theory of signatures,” according to which nature has revealed a plant’s medicinal properties through its form, also explains many uses of samples: pulmonary, or lungwort, owes its name and its use in the treatment of lung diseases to its spotted leaves, which evoked the lung’s alveoli. Hyssop is a digestive, antiseptic, and expectorant plant which purified lepers and sinners, whereas rue was thought to repel snakes and evil spirits: medieval medicine did not separate treatment for the body from that for the soul, and plans could have spiritual virtues.
Use and symbolism were often associated in the Middle Ages… in most medieval gardens…vegetables, simples, and flowers grew in the kitchen garden, while simples mingled with flowers in pleasure gardens.