The influence of leaf blanching with black polyethylene non-woven (PP) or white and black polypropylene foil (PE) used as soil mulching and blanching of leaves on yield, usefulness and biological value of cardoon leaf petioles were evaluated in the presented work. The effect of blanching duration of petioles (30, 25 and 10 days before leaves’ harvest) on the content of bioactive compounds was also estimated. The aim of the research was to evaluate the total yield of leaves, yield structure, dry weight, content of crude fibre, total sugars, L-ascorbic acid, chlorophyll, phenolic acids in conversion to caffeic acid, total flavonoides and DPPH activity in leaf petioles depending on the method and duration of leaves blanching. The content of apigenin, chlorogenic acid and cynarin in leaf petioles were marked with HPLC. Petioles of non blanched plants showed more dry weight and contained more L-ascorbic acid, chlorphyll, total phenolic acids and flavonoides than the uncovered ones. As a tendency it was observed that together with lengthening the blanching time from 10 to 30 days before harvest, the level of dry weight, crude fibre, total sugars, L-ascorbic acid and chlorophyll decreased. A reverse relationship was observed related to the blanching duration, as extending the time from 10 to 30 days before harvest, the content of total phenolic acids increased from 0.144 to 0.155% of fresh weight, while the content of flavonoides decreased from 0.662 to 0.352% of fresh weight. Lengthening blanching from 10 to 30 days before harvest of leaves decreased the content of apigenin and cynarin in petioles while increased the content of chlorogenic acid. The antioxidant activity DPPH did not depend on the method and duration of blanching. Unusual nutritional and medicinal benefits of cardoon petioles come from its rich and valuable chemical composition.