This paper proposes a general and minimal continuous model of root growth that aggregates architectural and developmental information and that can be used at different spatial scales. Methods: The model is described by advection, diffusion and reaction operators, which are related to growth processes such as primary growth, branching, mortality and root death. Output variable is the number of root tips per unit volume of soil. Operator splitting techniques are used to fit, solve and analyze the model with regards to ontogeny. The modeling approach is illustrated on a 2D case study concerning a part of Eucalyptus root system. Results: Operator splitting is helpful to fit the model. Basic knowledge on root architecture and development allows decreasing the number of unknown parameters and defining ontogenic phases on which specific calibrations must be carried out. Simulation results reproduce quantitatively the dynamic evolution of root density distribution with a good accuracy. Responsible Editor: Alain Pierret. A. Bonneu ? Y. Dumont ? H. Rey ? T. Fourcaud (B) CIRAD, UMR AMAP, TA-A51/PS2, boulevard de la Lironde, 34398 Montpellier Cedex 5, France e-mail: thierry.fourcaud@cirad.fr C. Jourdan CIRAD, UMR Eco& Sols, Montpellier, 34060, France Conclusion: The proposed root growth model is based on a continuous formalism that can be easily coupled with other physical models, e.g. nutrient and water transfer. The equations are generic and allow simulating different root architectures and growth strategies. They can be efficiently solved using adapted numerical methods.