Plants are immobile and cannot go searching for mates the way that animals can. Plants instead use other means of distributing their pollen to ensure their male gametes (contained in the pollen grains) reach a receptive female. Unfortunately, some plants use the wind to distribute their pollen, which causes problems for people with a pollen allergy. Plants that use this wind-pollination method share several characteristics, such as simple, dry flowers that lack nectar and colourful petals to attract pollinators like birds and insects. Also, wind-borne pollen is light and can drift considerable distances. Pine pollen grains, for instance, have wings that serve as floats enabling them to be carried hundreds of kilometers. Finally, wind-pollinated plants produce LOTS of pollen because the chance any of it will reach a receptive female plant is small.

Plants that use animals to distribute their pollen pose fewer allergy problems because their pollen is generally larger and heavier than wind-borne pollen and has surface features to help it get snagged in hair and feathers. Pollen from an animal-pollinated plant doesn't drift far on the wind, and animal-pollinated plants also produce less pollen than wind-pollinated plants because there’s a good chance of it reaching a receptive female. All these features combine to reduce the allergic risk posed by animal-pollinated plants.