Flowers may be small and inconspicuous, green and not showy. They produce enormous amounts of tiny pollen grains (hence wind-pollinated plants may be allergens, but seldom are animal-pollinated plants allergenic). They have large feathery stigmas to catch the pollen grains. They grow in low-diversity stands and are among the taller species in their communities. Insects may visit them to collect pollen, but they are not the most effective pollinators and exert little selection pressure on them.