Ikebana a piece's color combinations, natural shapes, graceful lines, and the implied meaning of the arrangement. Another common but not exclusive aspect present in "ikebana" is its employment of minimalism. Some arrangements may consist of only a minimal number of blooms interspersed among stalks and leaves. The structure of some Japanese flower arrangements is based on a scalene triangle delineated by three main points, usually twigs, considered in some schools to symbolize heaven, human, and earth, or sun, moon, and earth. Use of these terms is limited to certain schools and is not customary in more traditional schools. A notable exception
Ikebana kuge (供華). Styles of "ikebana" changed in the late 15thcentury and transformed into an art form with fixed instructions. Books were written about it, ""Sedensho"" being the oldest one, covering the years 1443 to 1536. "Ikebana" became a major part of traditional festivals, and exhibitions were occasionally held. The first styles were characterized by a tall, upright central stem accompanied by two shorter stems. During the Momoyama period, 1560–1600, splendid castles were constructed. Noblemen and royal retainers made large decorative "rikka" floral arrangements that were considered appropriate decoration for castles. When the tea ceremony emerged, another style was introduced for