Nature Note: Flowering Aquatic Plants
On land plants have developed elaborate mechanisms to ensure pollen passes from male flowers to female flowers through wind or intermediate pollinators and thus ensuring reproduction; water presents a different challenge. Pollen can not move through water as it can through air and the reliable insect pollinators are much less abundant. Most aquatic plants compensate by holding their flowers above the surface of the water. Once pollination has been completed the stem holding the flower might coil as in water lilies, pulling the flower down below the water surface and out of sight from seed and fruit predators.
A few plants actually pass pollen through the water. One such species is coontail, a common native underwater plant sometimes mistaken for Eurasian water milfoil. In this species, male flowers break off of the plant and float to the surface. Once there they drop pollen which sinks down onto the female flowers which remain below water. Despite the fascinating strategies that some species have developed, vegetative growth from existing plant material is still the most common form of reproduction.