Growth rate of leaves of winter barley (Hordeum vulgare L. cv. Efra) plant in thermal time correlated with the final length of the corresponding leaf (r = 0.66). The sum of effective temperatures corresponding to the time of growth of a particular leaf linearly increased with leaf insertion (r = 0.82). Phyllochron value in plants grown in the field with either natural or controlled photoperiod was dependent on phyllochron order, especially up to the double ridge stage (r = 0.89 and r = 0.74, respectively). The mean value of phyllochrons in the field variants showed a very good agreement with the value calculated on the basis of the change in day length at the time of seedling emergence.