Works depicting flowers and plants, whether as the major focus of a painting (as in a still life), part of an elaborate ornamental program (such as on a building or vessel), or as a small, background aspect of a work (as has been the case in thousands of paintings throughout art history). In Western art, flowers have historically been used to symbolize spring, rebirth, hope, and the ephemeral nature of human life. Many flowers have specific meanings tied to them; the rose, for example, has been associated with the Virgin Mary, as well as martyrdom (red roses), purity (white roses), and of course love. Trees, on the other hand, have been used to signify knowledge or its acquisition.