Flexibility of plants in the inter embankment zone makes them bend, to various degrees, under the force of flowing water. Determination of the mechanical properties is crucial for forecasting the behavior of vegetation and determining the hydrodynamic drag forces resulting from vegetation. This is also directly linked to the water table in the channel. Laboratory measurements were carried out for branches of willow, reed and alder, allowing for the determination of modulus elasticity, modulus of non-dilatational strain, limit of elasticity for the twigs, and their humidity. Mechanical properties of samples under investigation mainly depended on the humidity and species of plants. Experimental results confirmed considerable variability of parameters even within samples coming from a single plant.