The objective of this work was to model the architecture and growth dynamics of the oil-palm root system. The morphological and functional unit of the root system, called "root architectural unit" and its development sequence enabled us to establish the basis of a mathematical formalization of the root system architecture. The topology of the branched structures and the processes of growth, branching and mortality were described and modelled by stochastic processes (graph model, automata, laws of probability). The models obtained were then combined with geometrical parameters in an overall mathematical model: the reference axis. Simulation of this model provided 3-D numerical models. Validations of the overall model based on comparing the 3-D numerical models with observed root systems, appeared satisfactory.