CONTEXT: Planting fruit trees in a market gardening system creates a mixed fruit tree - vegetable system with the potential to address certain environmental issues. However, it results in a complex system where labor has to be allocated between the two activities. OBJECTIVE: Our objective is to simulate possible trajectories for a perennial transition from market gardening to mixed fruit tree - vegetable systems, in order to study the required trade-offs. METHODS: We modeled the transition using viability theory, a framework with states, controls and constraints that guarantees sustainability along a transition trajectory. It was used in two iterations, the first step computing a target to be reached during the second step. Trajectory samples were computed from the sets of viable states at each time step.RESULTS AND CONCLUSIONS: In order to guarantee sustainability, at the end of the transition process the farm must not only respect the constraints but belong to a subset of the domain they define. The study of viable trajectories shows a trade-off between capital and working hours, and thus different suitable strategies for the timing of orchard planting and the choice of crop rotations. Some strategies present bottlenecks where the flexibility of the farm is greatly reduced.