Quality aspects of cut chrysanthemum, such as weight of the plant and number and size of flowers, have been widely studied. However, these are seldom integrated in a single model. A functional-structural model, GreenLab, was used to simulate the geometrical features of chrysanthemum with underlying rules on biomass production and allocation. In this paper, model calibration was conducted based on data from a climate room experiment. Chrysanthemum `Reagan Improved¿ was grown at 16°C and 380 ¿mol m-2 s-1 PAR, with 14 days long day (LD) period (19 h of light), followed by short day (SD) period (11 h of light) until harvest. Detailed measurements included weight and size of leaves and internodes in the main stem, and diameter of flowers, weight of all leaves and that of stems for side shoots. Non-linear least square method was applied to fit the parameters of the GreenLab model, such as the sink strength of the organs. New features introduced into GreenLab are: (1) number of primordia to fill the gap between development and growth; (2) delay function of growth to simulate the top-down flowering sequence; (3) additional sink of growing internodes on main stem to simulate their strong growth after terminal-bud removal; (4) two phases for individual flower growth. Realistic 3D chrysanthemum was simulated, which is a starting point for introducing effects of varying cultivation conditions.