Complete flowers are flowers that have all four main components: sepals, petals, pistils and stamens while incomplete flowers lack at least one of those elements. The difference between complete and incomplete flowers is structural rather than chemical in nature. The different parts of flowers serve different purposes, but like the human appendix, not all parts are essential for helping flowers carry out life functions.
The various parts of flowers have diverse roles throughout the life of the plant. Sepals are among the most recognizable components of many plants, and provide assistance to young growing plants from the time they sprout. Sepals are often green, and form at the base of flowers. They are leaf-like in appearance and, in addition to giving plants their unique look, help to keep delicate flowers protected as they grow. Flowering plants all have sepals, but sepals are rarely found on plants that do not produce flowers. Petals are also structural components of complete flowers. Most have vivid colors and form a variety of shapes and patterns. Petals serve the purpose of attracting pollinators, such as insects and birds. Stamens are found only on complete male flowers; these structures contain two subunits called the anther and filament. Pistils are found on female complete plants. They are reproductive organs where fertilization takes place.