Appearance, expansion, and duration of individual leaves are critical determinants of plant canopy growth and development. Accurate modeling of these processes has an impact on estimating canopy light interception, photosynthesis, and accumulation of dry matter and yield. Most potato models use a ‘big leaf' approach that simulates increases in total canopy leaf area based on empirical relationships with environmental inputs and plant nutritional status. In order to improve the capability of these models, mathematical expressions for individual potato leaf appearance, expansion, and duration were developed. Potential leaf appearance rates were quantified using a non-linear temperature response function. Leaf expansion was modeled as a function of leaf physiological age, temperature, and assimilate supply, and leaf duration was expressed as a function of physiological age of individual leaves. These equations were integrated with existing subroutines for potato phenology and carbohydrate partitioning in order to simulate whole potato crop growth and development. A leaf photosynthesis model coupled with models for stomatal conductance and energy balance is being integrated with the model. Preliminary testing will be performed by comparing the model simulations using whole plant gas exchange, growth, and development observations from SPAR (soil-plant-atmosphere research) chamber experiments conducted in Beltsville, MD in 2004.