Temporal diffusion spectroscopy (TDS) can be used to infer sizes of cells in samples. It relies on a geometric model to relate the MRI signal to the cell sizes. Garlic stem collenchyma tissue has long cells which might be modelled as cylinders. We compared a cylindrical and spherical geometric model in temporal diffusion spectroscopy to determine how important the geometrical model was for garlic stems. The inferred diameters of cells in the garlic stem (4μm-6μm) were not statistically different when using the two different geometric models. This is the first step toward understanding the importance of geometric models for TDS.