From earliest times meanings have been associated with flowers and the emotional effect upon those who receive them. The writings of Aristotle, Plato, Socrates and many other early philosophers, circa 350 B.C., identify flowers and plants and employ them as metaphors in their philosophical treatises.
Egyptian hieroglyphics and tomb paintings illustrate the giving of flowers as symbols that hold meanings for the giver and the reciever.
Shakespaeres's characters often spoke of flowers and their meanings to inform the audience subtly about the plot, underscore the meaning of the spoken line, and to add the visual emphasis of that meaning to the action on stage. Consider Ophelia noting the meaning of the flowers in her hand in Hamlet.
Early European paintings, particularly the Flemish masters Jean Paul Reuben, Jan Breughel, and many others in the 16th and 17th centuries, held not a casual combination of objects within the painting. Rather each item and each flower had its own symbol and meaning telling the viewer the story behind the painting, the occasion, and the character of the principals in it.
For more information see The Language of Flowers and Flower of the Month pages.