Pecan trees bloom in the spring, usually in late April or early May, although the exact time depends on the cultivar. The trees produce separate male and female flowers on the same tree. The flowers rarely bloom at the same time, however; one tree must pollinate with another cultivar to produce a crop of nuts.
The pecan tree's flowers look rather insignificant. The male blooms consist of greenish-yellow catkins that resemble tassels. The female flowers consist of star-shaped growths that appear on the tips of new branches.
The male pecan flowers bloom first; the female flowers often bloom after the male flowers have finished blooming. Since the males often shed their pollen before the female flowers are ready, the female flowers must get their pollen from another variety of pecan tree that has a later male bloom time.
Pecan trees primarily pollinate via the wind. All it takes for pollination to occur are a few hours of good weather, the right humidity and a breeze to move the pollen between the male and female flowers.