Timing is everything. There is just a matter of 2-3 days in which the flowers can be pollinated. Pollen is taken from the anthers of one plant and put on the stigmas of the other. The plant cannot self-pollinate, and if there was only one plant it would not be pollinated. Two plants have to blossom at the same time and pollen taken from the anthers of plant #1 and put on the pistil of plant #2. Then, pollen from plant #2 put on the flower of plant #1. Each day during this time, the plants are checked for new blossom and cross pollinated. In nature the bees and flower would have to be on an exact schedule. Timing is everything.