Coniferous forest or ‘taiga’ is able to exist in regions where the growing season is too short to support deciduous woodland. Because their leaves do not fall, but survive throughout the winter, coniferous trees are ready to begin photosynthesis without any delay and as soon as temperatures become favourable. Moreover, the coniferous type of fructification has the advantage that it is pollinated one year and dispersed the next, whereas deciduous trees have to complete the process within a single season. Length of growing season—that is, the number of months with temperatures above the threshold for growth—is clearly the most significant factor controlling forest types.