Technical Abstract: Background and Aims: Since Grey presented the concept of the phytomer in 1879, the phytomer concept has been useful for understanding plant development and architecture. Commonly the phytomer is viewed as a vegetative unit consisting of a leaf, node, internode, and axillary bud, with this unit repeated within and among shoots. We have extended this definition to include the root nodal bud and the inflorescence structure. Based on available knowledge and objectives, models may not fully incorporate the phytomer concepts, rather some phytomers may be aggregated into a single component such as a spike or grain component. This paper describes how the use of a Composite Pattern in an object-oriented (OO) design facilitates implementation of different scales from the phytomer to a mixture of single and aggregated phytomers for different plant components. The objectives of this paper are to provide detail on the conversion of the botanical abstraction of a phytomer into OO design and to present a proof-of-concept prototype OO plant model, CANON, so called because the interplay of repeating phytomers is analogous to the repeating melodies of a musical composition called a canon. Methods: In CANON the canopy is built by the addition of phytomer units consisting of a leaf, node with internode, axillary bud, root, spikelet and floret. A phytomer has a consistent type of communication with adjoining phytomers, which matches the OO structural composite design pattern described by Gamma et al. (1994), where objects are represented in part-whole hierarchies by tree structures, with uniform treatment of individual objects and compositions of objects. At any point, the following hierarchy is viewed as a single entity thus allowing parts of the hierarchy to be replaced with a single object, without affecting the preceding hierarchy. Key Results and Conclusions: This approach allows specification of sub-models of different levels of detail which could be selected at implementation or run-time. The phytomer concept of building plants meshes naturally with the Composite Design Pattern which, by providing a consistent interface between components (phytomers or aggregates), simplifies the coding and reduces potential for errors. The design provides open-ended recursion of phytomers, which facilitates easy implementation of different determinate and indeterminate plant species.