As the name implies, these are plants that are free floating at the surface or have leaves that float. They typically have some sort of root system that hangs below the plant and filters the water for nutrients. Two common undesirable or nuisance floating aquatic plants (not including algae which is discussed individually in the Algae Solutions page) are Duckweed and Watermeal. These two species of aquatic plants can cover a pond and create a very unappealing pond or lake. They also block out sunlight from reaching the rest of the water column which limits growth of other aquatic plants and can limit the amount of oxygen available for your fish. Some more desirable floating aquatic plants, in moderation, are Water Lily (Lily Pads), Watersheild, and Spatterdock. These plants are considered more desirable because they enhance the aesthetics of a pond and create nice flowers. However, they can overrun a pond and become undesirable if not controlled.
Duckweed (Lemna minor) is a small, green, round or oval aquatic plant that floats at the surface with a root that hangs below. Duckweed is transferred or spread by humans and wildlife (ducks, geese, turtles, etc.). It can quickly spread and cover an entire pond, blocking sunlight for other plants and causing an unappealing pond. Common treatments are with a diquat (contact herbicide) which turns duckweed brown on contact or fluridone (non contact herbicide) which turns the duckweed white. Grass Carp will also eat duckweed.
Watermeal (Wolfnia spp.) is smaller than duckweed and looks like small green seeds with no roots that hang below. Watermeal will feel gritty between your hands and fingers. Watermeal can be spread by humans and wildlife into new areas. It can also spread quickly and cover an entire pond blocking sunlight and causing an unappealing pond. Common treatments are with a diquat (contact herbicide) which turns duckweed brown on contact or fluridone (non contact herbicide) which turns the duckweed white. However, watermeal can be more difficult to treat than duckweed.
Fragrant Water Lilies (Nymphaea odorata) are a great example of beauty in moderation. Lily pads can greatly enhance the beauty of a pond or water garden with the green pads and the flowers, but they can also quickly overtake a pond if not monitored. They can be held in check by simply pulling the pads out. They have rounded leaves about 6-12" with a cleft or cut to the center. The underside is a purplish red color. A white, fragrant flower is also produced.
Water Hyacinth (Eichhornia crassipes) is an invasive plant species that originated from Brazil. It can quickly spread and take over an entire pond; therefore, it is often classified as undesirable. It is characterized by the prominent purple flower. The upper petal of the flower has a yellow spot surrounded by purple. If this species is in your pond, it is important to keep it from spreading too rapidly with treatment or pulling the plants out.
Watersheild (Brasenia schreberi) has floating lobed leaves similar to the Fragrant Water Lily, but without the cleft and the leaves are much smaller, typically only about 4" long and 3" wide. The stem and undersides of the leaves are purple and are covered with a thick, gelatinous coating. This can be a desired species depending on personal taste and if it has not overrun the pond.
Spatterdock (Nuphar polysepala) is another rooted plant with floating leaves and flowers. Yellow, ball shaped flowers bloom during the summer months. The leaves are large (12") and can be round or heart shaped with rib down the center and a cleft. It is a great species for fish and wildlife because it serves as a food source and habitat.
These pages are reprinted from www.gotalgae.com, courtesy of www.kascomarine.com
