This paper presents studies on the life history evolution of plants carried out by experimenting with a multi-agent platform of generic virtual plants. The conducted simulations address the trade-off between resource allocation to vegetative and reproductive structures. The trade-off is pointed out by evolutionary runs selecting for one of the two traits. It is further shown that the introduction of an age at maturity is an effective measure to enhance both life history traits. A third series of experiments highlights that competition in plant communities has an impact on the trade-off. Depending on the competitive pressure, plants evolve more investment of resources into growth than into reproduction. The results corroborate some hypotheses of life history theory.