The aim of this chapter is to introduce the simulation of plant structures and architectures using the botanical automatons (including deterministic and stochastic development). Deterministic development with constant phyllochron is rare, occurring in some single-stemmed plants, while most branched plants have variable phyllochrons, resulting in diverse phytomer production. The GreenLab model simulates meristem activity stochastically with parameters a, b, and c, representing branching, development, and viability rates. It uses development cycles (DCs) to measure an axis’s chronological age, offering both chronological and topological visualization modes. The model produces cohorts of organs and a potential structure that contains the history of development. Monte Carlo simulations are used to estimate axis branching and phytomer distributions, and the crown analysis method infers developmental parameters from plant architecture, aiding in data restoration. The model operates in matrix mode for element production and list mode for creating a dual botanical automaton for three-dimensional (3D) plant simulation in computer graphics.