Results of laboratory studies based on a field experiment conducted in 1993-1995 on soil developed from light loamy sands were analyzed. The experiment was set up according to the randomized subblocks method, in 3 replications. The following three factors were examined: two culti-vation technologies (with PE-foil and traditional one); four potato cultivars (Aster, Irys, Lotos, Malwa); five nitrogen fertilization levels (0, 50, 100, 150, 200 kg ha-1) on the background of constant phosphorus-potassium fertilization (120 kg P2O5 and 180 kg K2O ha-1) 25 t ha-1 of manure. Potato plants were crossing over the full vegetation cycle in the above-mentioned years. Phenophases were succeeding in particular sequences specific for potato and cultivar. Differences in seasonal rhythms at various objects were observed. Weather conditions influenced acceleration or delay of some phenological occurrences. Essential dependence appeared with cultivation technologies and genetically properties of cultivars, at all development stages. The time of flowering of potato plants turned out to be dependent also on wind speed during the period of May-August, and the time from emergence to the beginning of leaf wilting – on rainfalls during the same period. The sum of May-August rainfalls and mean air temperature also determined the length of vegetation period.