L-system notation was used to describe mature leaf morphology in populations of conventional, afila, tendril-less and parsley-leaf peas. Structural modules of leaves were assigned one of eleven state symbols according to their branching potential, i.e. the number and arrangement of rachillae and/or tendrils or leaflets to which each would give rise after one branching iteration. State transitions at successive iterations were examined across genotypes with respect to location along the leaf and node of insertion. Leaf branching patterns were more complex and more variable at higher nodes. Transition outcomes decreased in complexity from the base to the tip of the leaf. The first transition was the most variable; subsequent development of the leaf was more deterministic. Lateral appendages were more likely to branch than central ones. Afila and tendril-less mutations increased the complexity of the first transition outcome over conventional leaves. Parsley-leaf pea leaves were more complex, but less variable than afila leaves. Results are discussed in relation to Young's (1983) model for pea leaf morphogenesis.