Professional recommendations vary for the number of hives needed for good pollination, but for these crops 1-2 colonies per acre is commonly used. If the pollen is compatible, fertilization of the ovule and seed formation occur. Generally, more seeds develop when large numbers of pollen grains are transferred. Seeds, in turn, stimulate surrounding ovary tissue to develop so that, for example, an apple with many seeds will be larger than one with fewer seeds. In this way, good pollination improves both fruit yield and size.
Many insects visit flowers to collect pollen and nectar as food.
As they forage, these insects spread pollen grains among flowers, accomplishing pollination. Many flowers offer sugary liquid nectar as an added enticement for these pollinating insects. Among insect pollinators, bees are especially efficient because they eat pollen and nectar exclusively, visit many flowers of the same species during a single trip, and have hairy bodies which easily pick up pollen grains. There are over 3000 species of bees in North America. Most of these are solitary bees, but a well-known minority are social , that is, they live together in colonies and cooperate in colony tasks.