Seasonal changes in the biomechanical properties of Elodea canadensis Michx

•Seasonal changes during the Elodea canadensis Michx. life cycle influence the plant’s biomechanical properties.•A stem diameter, without information about the stage of plant development, is not a reliable indicator of changes in biomechanical parameters.•The biomechanical traits of E. canadensis do not differ significantly between the bottom and upper parts of the stem. The biomechanical properties of a common invasive aquatic plant in Polish rivers, Elodea canadensis Michx., were investigated. Tension and three-point bending tests were conducted under submerged conditions for the entire life cycle of the plants. The results showed statistically significant seasonal changes in the biomechanical properties of E. canadensis depending on the plant growth stage. In the mid-summer season, the maximum values of biomechanical traits were observed. In August, E. canadensis was characterised by the highest moduli of elasticity: 141.20 MPa in flexural modulus and 37.82 MPa in Young’s modulus. At the same time, the stem was stiffest, and its flexural rigidity was 12.45 N mm2. After this period, a decrease due to plant senescence was observed, and finally, the stiffness decreased to 3.67 N mm2. The results showed that E. canadensis adapts to the hydrological conditions in rivers with respect to its ability to return to its original shape after bending. Moreover, the investigated characteristics did not differ significantly between the bottom and upper parts of the stem. Finally, the studied changes in the biomechanical traits of E. canadensis, as a representative of aquatic plants, highlight the value of accounting for such characteristics and their seasonal changes.