Many types of plants grow in water. Ponds and lakes, seas and oceans support a variety of plants adapted to living in an aquatic environment. Lotus, water hyacinth, duckweed, and algae are just a few examples of plants that grow above, on or below the surface of the water. Interestingly, many house plants can also be grown in water alone, the stems of which root easily in water.
Algae are primitive aquatic plants. Some, such as planktonic algae, are microscopic; while others, like Spirogyra, Pithophora, and Oscillatoria grow as filaments, forming large mats at the surface of the water or fields along the bottom. Still others, such as Chara (also known as muskgrass) and Nitella, resemble higher plants with stems and leaf-like structures.
Plants that grow almost completely under water are known as submerged plants. Submerged plants are usually rooted to the bottom, however, the roots are used only as anchors. These plants get nutrients from the water itself through their leaves and soft stems. They are strong oxygenators for ponds and lakes and help reduce algae growth by competing with algae for nutrients.
Pondweeds, Naiads, eelgrass, Hydrilla, Elodea, watermilfoils, parrotfeather and fanwort are all examples of submerged plants.
Emergent plants are also known as marginal plants, because many species tend to grow along the edges, or margins, of ponds or lakes. The plants grow underwater, but sprout leaves and flowers that emerge from the water into the air above.
Cattails are typical of a marginal plant. Other examples include iris, horsetail, pickerel weed, arrowhead, pennywort, water primrose and a variety of sedges, reeds and rushes. Additional emergent plants will grow in deeper water and produce leaves that often float on the surface. These include water lilies--both hardy and tropical forms--and lotuses.
Floating plants live on the surface of the water, requiring no soil for nutrition or anchoring. The leaves and flowers are above the water, forming a vegetative "raft" with roots that extend into the water. They float freely and are often moved about by wind and water movement.
These can range from very tiny plants, such as duckweeds, with each individual plant being less than 1/4 inch, to large mats of colorful water hyacinth and water lettuce. Other types of floating plants include bladderworts, featherfoils, salvinias, mosquito fern and watermeal.
Many house plants can be grown in only water. Cuttings taken from these plants can be placed in water in a vase or glass and will root in a short period of time and continue to grow well. Examples are Dracaena, Philidendrons, arrowhead vine, Pothos, Chinese evergreen, jade plant, Dieffenbachia, and several types of ivy.