2D Finite Element (FE) Analysis of tree overturning was carried out. The main objective was to determine the effect of particular roots on anchorage strength in two contrasted soils and to discuss acclimation of root growth with regard to mechanical constraints. The FE model was based on the description of herringbone- like root patterns. Tree overturning simulations were performed applying a lateral displacement to a rigid stem. The results showed that lateral roots are the main components of tree anchorage in clay-like soil whereas the taproot plays a more significant role in sand. The modes of failure were different in the two soils, resulting in different root-plate shapes and rotation axis positions. Anisotropic secondary growth as a response to mechanical perturbations was also discussed based on the calculation of von Mises' stresses at the surface of the root elements. In conclusion, we propose a new concept whereby Functional Structural Plant Models are linked with Biomechanical Models in order to test hypotheses concerning tree growth acclimation to mechanical stresses.