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Control of nitrate content and other growth characteristics of leafy vegetables such as greenhouse lettuce is an increasingly topical subject in a European context. This preliminary study focuses on the control of characteristics in greenhouse lettuce at harvest time on the basis of dynamic optimization techniques in which a novel lettuce growth model of the plant is embedded. In order to gain insight in the growth model itself first various constant input responses are presented, followed by some results of a more challenging problem in which dynamicinput trajectories are assumed. The 'step-by-step' approach starts with a concise model definition and progresses via the constant input response and the definition of an appropriate cost (defining optimality) towards a dynamic optimal solution. The method leads to some interesting design considerations and suggestions for further research, which are made in a concluding section.