Since 1879 when Grey presented the concept of the phytomer, much work has gone into understanding how plants build their canopies by the addition, growth, and subtraction of phytomers.  While various definitions of phytomers have been proposed, most commonly the phytomer unit is viewed as consisting of a leaf, node, internode, and axillary bud, with this unit being repeated within and among shoots.  This dynamic interplay of phytomers can be viewed as analogous to a composition of music called a canon (a familiar simple form being a round) where individual phytomers repeat a part against and with other phytomers as do the melodies of a canon. The phytomer concept has proven to be a useful botanical abstraction for providing a foundation to understand plant development and architecture. However, few simulation models (e.g., SHOOTGRO) are based on this botanical design, and historically have been written in procedural programming languages such as FORTRAN. The objectives of this work is first to clearly describe the phytomer approach to how plants build their canopies from vegetative through inflorescence phytomers (using temperate cereal crops of wheat and barley to illustrate this), then translate this botanical abstraction to an object-oriented design (OOD), using the composite pattern, that can be implemented into a variety of computer languages, and last to give a simple “proof of concept” of the OOD developed and referred to as CANON.