Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms (non-flowering) or angiosperms (flower-producing). However, flowering anemophilous species do not develop scented flowers, nor do they produce nectar. This distinguishes them from entomophilous and zoophilous species (whose pollen is spread by insects and vertebrates respectively).
Male and female reproductive organs are generally found in separate flowers, the male flowers having a number of long filaments terminating in exposed stamens, and the female flowers having long, feather-like stigmas.
Pollen from anemophilous plants tends to be smaller and lighter in weight than pollen from entomophilous ones, with very low nutritional value to insects. However, insects sometimes gather pollen from staminate anemophilous flowers at times when higher protein pollens from entomophilous flowers are scarce.
Also anemophilous pollens may also be inadvertently captured by bees' electrostatic field. This may explain why, though bees are not observed to visit ragweed flowers, its pollen is often found in honey made during the ragweed floral bloom. Other flowers that are generally anemophilous are observed to be actively worked by bees, with solitary bees often visiting grass flowers, and the larger honeybees and bumblebees frequently gathering pollen from corn tassels and other grains.
Almost all pollens that are allergens are anemophilous. Other common anemophilous plants are grass species, conifers, sweet chestnuts, and members of the hickory family. Entomophily is a form of pollination whereby pollen is distributed by insects, particularly bees, Lepidoptera (e.g., butterflies and moths), flies and beetles.
Entomophilous species frequently evolve mechanisms to make themselves more appealing to insects, e.g., brightly-colored or scented flowers, nectar, or appealing shapes and patterns. Pollen grains of entomophilous plants are generally larger than the fine pollens of anemophilous (wind- pollinated) plants. They usually are of more nutritional value to insects, which may use them for food and inadvertently spread them to other flowers. Entomophilous species include the sunflower, orchid, and cycad.