Natural plants provide an important role in the health of a pond. They provide shade, act as a sediment filter and reduce erosion on shorelines. Natural plants also play a role in the life cycle of fish by providing oxygen, a sheltered nursery area and food to aquatic insects. Plants that grow in water (called aquatic plants) are categorized as emergent, submerged or floating plants.
Emergent plants are also known as marginals. They usually grow along the shoreline of a lake or pond and are rooted in the muddy soil below the water line. The stems of emergent plants are usually rigid and are above the waterline. Other emergent plants, such as lilies, may grow further away from the shoreline but still have roots immersed in the mud with their leaves still afloat on top of the water.
Bog plants are also emergent plants and have minimal light requirements for growth. The University of Illinois Extension reports that some bog plants may only require approximately three hours of sunlight and provide interest for areas with limited sun exposure.
Examples of emergent plants are cattail (Typha), sweet flag (Acorus calamus), canna (canna americanalis), elephant ears (Colocasia esculenta), southern swamp lily (Crinum americanum) swamp hibiscus (Hibiscus moschuetos), water pennywort (Hydrocotyle americana), spider lily (Hymenocallis caroliniana) and Japanese water iris (Iris ensata).
Submerged plants are also known as submersed plants. They have their root system anchored into the soil at the bottom of the pond. The entire plant remains below the surface of the water due to their soft, pliable stems. Submerged plants produce oxygen, reduce algae and provide shelter for fish.
Examples of submerged plants include American pondweed (Potamogeton nodosus), coontail (Ceratophyllum demersum), curly-leafed pondweed (Potamogeton crispus), egeria (Egeria densa), fanwort (Cabomba caroliniana), Illinois pondweed (Potamogeton illinoensis), marine naiad or brittle naiad (Najas marina) and sago pondweed (Potamogeton pectinatus).
Floating plants are also known as floaters. They are not rooted in soil and may float freely on the surface of the water with roots that are below the water's surface. These plants are considered to be the ground cover of aquatic plants, according to the University of Illinois Extension. These floaters can be complementary plants for water lilies or other plants that float on the surface. Floaters can become invasive, requiring occasional removal of some plants.
Floating plants include fairy moss (Azolla caroliniana), lesser duckweed (Lemna minor), water poppy (Hydrocleys nymphoides), mosaic plant (Ludwigia sidioides), parrot feather (Myriophyllum aquaticum), water hyacinth (Eichornia crassipes), mosquito fern (Azolla), bladderwort (Utricularia) and water meal (Wolffia).