For nut trees to produce nuts, you'll need two or more different cultivars, since they require cross-pollination for maximum productivity. Walnut trees don't bear fruit until they are between four and 12 years old and that is determined by the cultivar. Pecan trees are monoecious, meaning that both male and female flowers are on the same tree. Female flowers (pistilate) are found at the end of current season growth and male flowers (growths) are found at the end of last season's growth.
The growths are easy to spot because they hang on the tree in early spring. A single increase can produce up to 2.64 million pollen grains. Only one grain of pollen is required to produce a nut. An increase can produce enough pollen to pollinate flowers and produce 50,000 pounds of medium-sized nuts.
An average producer tree is likely to produce several thousand branches, further emphasizing the amount of pollen that could be produced. Usually, an individual nut tree blooms and sheds pollen at different times. Naturally, this method helps to promote the diversity of nuts, which become new nut trees in nature. For adequate cross-pollination between nut trees, it is strongly recommended to grow at least one of each type.
Walnut trees bloom and give off pollen at different times, making the pollination of walnut trees different from that of fruit trees.