This paper introduces a solution to compute Lsystems on parallel architectures like GPUs and multi-core CPUs. Our solution can split the derivation of the L-system as well as the interpretation and geometry generation into thousands of threads running in parallel. We introduce a highly parallel algorithm for L-system evaluation that works on arbitrary L-systems, including parametric productions, context sensitive productions, stochastic production selection, and productions with side effects. Further we directly interpret the productions defined in plain-text, without requiring any compilation or transformation step (e.g., into shaders). Our algorithm is efficient in the sense that it requires no explicit inter-thread communication or atomic operations, and is thus completely lock free.