The author presents the results of studies which were the subject matter of 14 published papers. The studies were concerned with the determination and assessment of the mechanical properties of the stems of winter rape varieties. A broad range of test methods, as well as a variety of plant growth conditions were applied, including provoked plant lodging. Measurements were taken at the particular phenological phases of the plants. Also, the studies took under consideration the determination of the structural parameters of rape stems, which, apart from being indispensable for the determination of the mechanical parameters, helped in the assessment of the differentiated stem structure. The results of the studies permitted, with the passage of time, to eliminate certain of the methods used for the determination of the strength characteristics of rape stems, and to indicate the choice of one value which proved to be easier to determine, also in the course of an experiment, and did not require calculations. The studies showed variability of static and dynamic tests in the case of stem shearing energy determinations. That conclusion, at the final stages of the experiments, permitted the application of the dynamic shearing energy in the assessment of the variability of the plant mechanical properties. Therefore, when the X-ray tests were applied for rape stem analysis, only the dynamic test was used for the strength characterisation of the stems. The studies permitted the formulation of the conclusion indicating the occurrence of a minimum of the shearing energy corresponding to the stem unit cross-section located at the first branching. That in turn permitted, in further studies on rape stems, the limitation of measurements to the characteristic spot. The studies provided strength characteristics for stems of plants grown under extremely varied conditions, both as to the dosage of nitrogen fertilisation applied, provoking their lodging, and to the planned specific sowing density (number of plants per square meter). The results of the experiment involving a broad spectrum of investigative methods, which provided a number of mechanical parameters used in the testing of rape plant stems grown under varied agrotechnical conditions, showed the relation between the resistance of rape plants to lodging and the mechanical properties of their stems. In recent years, basing on the results of this method for the study of the mechanical properties of rape stems, a new method was developed for the determination of the mechanical properties of black currant shoots, using the static test, as well as new method for the study of the mechanical properties of the stems of pea varieties, determined by means of the static and dynamic tests. The result of that last study is the determination of significant intervarietal differences which also confirmed the applicability of the methods applied for the assessment of the mechanical properties of the objects under study.