Not only does a flower contain the parts necessary for reproduction, it also is very flashy about advertising its rich supply of nectar and pollen. Flowers trade sweet nectar and protein-rich pollen in return for the service that insects and other creatures perform: pollination. Pollination is simply the transfer of pollen grains from an anther to a stigma.

For many plants, the production of seeds that will grow depends on the transfer of pollen from one flower to another flower of the same kind. Most pollination occurs when insects and other creatures brush against the pollen-bearing parts of a flower and pick up pollen. When the creature goes to another flower for more food, some of the pollen from the first flower sticks to the second flower. In this way, the flowers are pollinated.

In general, pollinators are attracted to plants that offer an abundance of food. Different insects are attracted to different types of flowers depending on color, scent, and size. Bees see higher colors of the human visible spectrum plus ultraviolet and tend to prefer blue, purple and yellow flowers that have a sweet scent. Butterflies are attracted to orange, yellow, pink and blue flowers that have a large landing pad. Moths are active at night, requiring flowers that are open and providing nectar at night. Large, white flowers are particularly easy for moths to see at night.

Although insects are responsible for the majority of pollen being transferred, pollination occurs in other ways. Creatures other than insects seeking nectar, like birds and bats, can also transfer pollen. Wind and water are other sources of pollination.

When the pollen grains that have been transferred to the stigma germinate, the flower becomes fertilized. After fertilization, the seeds are produced, and the ovary wall of the flower becomes the fruit.

About one-third of the total human diet is derived directly or indirectly from insect-pollinated plants. An estimated 80 percent of insect crop pollination is accomplished by honey bees. Honey bees are needed to pollinate a variety of fruits, berries, vegetables, tree nuts, oil seeds and legumes.