Remote sensing techniques with Synthetic Aperture Radar (SAR) provides detailed information of the electromagnetic scattering behaviour of their targets. It is broadly used for agricultural monitoring due to their all-weather acquisition possibility. Based on the nature of SAR systems, they are known to be sensitive to physical changes in the targets, such as plant growth. An uncertainty analysis for a plant morphology based electromagnetic scattering model is assessed in this study. The global sensitiveness of the model to the input variables are tested with respect to their total Sobol' indices. This helps to understand the parameters for each growth stage and polarization channel, which can be used to reduce the complexity of the scattering model.