A method of determining a pressure parameter of a plant sample (1) comprises the steps of subjecting the plant sample (1) to a clamp pressure (pclamp) created with a clamp device (10), measuring at least one pressure response value (pp) of the plant sample (1), which depends on the clamp pressure (Pclamp)/and determining the pressure parameter on the basis of the at least one pressure response value (pp), wherein the clamp pressure (pclamp) is adjusted, such that the plant sample (1) has a viscoelastic pressure response to the clamp pressure (pclamp). Furthermore, an apparatus (100) for determining a pressure parameter of a plant sample (1) is described.