This paper introduces JEcoSys, an extensible framework developed in Java to generate interactive simulations of plants. JEcoSys uses a simple physical model of plants, based on dynamic constraints, and pre-computations to achieve realism and efficiency during animation. The framework also includes a force field based technique to model the interaction of plants with different agents, that can simulate natural phenomena such as wind and rain. Experimental results show that JEcosys is able to simulate complex scenes containing hundreds of tufts of grass and flowers in real-time.