The present study is concerned with determining the cutting energy in dynamic tests, and the bending stress, shearing stress, and cutting energy in static tests for stalks of winter rape of the Jupiter, Jantar, and Jet Neuf varieties. A considerable variability was observed in the mechanical parameters of winter rape stalks, along the length of the stalks as well as in the course of the phenological stages of the plants. The studies also showed differentiation between the varieties. The character of changes in the values of the mechanical parameters along the length of the stalk is described by square polynominals. An evaluation is made of the effect of the stalk cross section surface area and of the stalk density on the variability of the mechanical properties of winter rape stalks in the course of the development of the plants. It was found that the stalks of the Jupiter variety were characterized by the lowest density as compared to those of the Jantar and Jet Neuf varieties. Also, the spacing of plant rows and the number of plants per m² were found to have a significant effect on the variability of the mechanical properties of the stalks of the Jupiter variety.