Timothy (Phleum pratense) is the most widely grown sown grass species for silage and hay production in the Nordic countries; it is also common in many other areas with a cold maritime climate. Research on timothy has identified many environmental factors and plant characteristics that determine timothy growth. However, much of the literature that analyses timothy growth presents only qualitative estimates of the importance of the different growth-determining factors. Here we present a review of quantitative information on timothy. Moreover, we analyse to what extent this quantitative information is sufficient to permit the construction of a simple process-based model of timothy growth. We then use such a model to identify the major growth-determining factors. Simulations with the model showed that the major processes to be elucidated in future research on timothy are tillering dynamics and the formation and loss of leaves from tillers. We conclude that a combination of literature review and analysis by means of simulation modelling, such as we attempted here, is an effective approach to identify and prioritize research goals.