Submerged water plants : The plants that produces oxygen under water
Plants that produces oxygen under water to help keep the pond in balance. Should be planted completely submerged.
Submerged water plants are the unsung heroes in the war against green water, the one battle all pondkeepers are sure to face sooner or later. Important to water quality as well as water clarity, underwater plants help filter unwanted nutrients and add important oxygen to the water during the day. Besides their usefulness, many are highly decorative as well. Some have finely cut foliage while others are long strap-like creatures that undulate in the current. Certain submerged plants were once popular in aquariums, but having become troublesome weeds in natural lakes and streams, may be unlawful to sell or keep under applicable
laws. Fortunately, alternatives to those prohibited plants are available that are helpful to the pond ecology.
Underwater plants are sometimes referred to as “oxygenators” because they add oxygen to the water in the pond. This label is a bit of a misnomer, since they produce oxygen only during the day.At night, submerged plants reverse the process and remove oxygen from the water. Many marginal pond plants have submerged forms often sold as oxygenators, but they often do not perform in the pond as they do in the fish tank.
Underwater plants vary greatly in their foliage and flower habits. They generally fall into three groups. Some, such as mermaid’s fan (Proserpinaca palustris) and Ranunculus, have both submerged and emerged foliage, each very different. Others, such as Cabomba,
have only submerged leaves but float their flowers on or above the water surface. Still others, such as Najas and hornwort (Ceratophyllum), have both submerged leaves and flowers.
Submerged plants with floating flowers often bloom in late spring or early summer, sometimes continuing intermittently throughout the summer.Although each blossom may be very small, a large grouping can make an attractive addition to the early summer pond,
when waterlilies have only just begun to flower, or to accompany water hawthorne (Aponogeton distachyus).
Foliage of submerged water plants is very distinct from that of emerged plants. Some leaves are thick and strap-like,while others are very thin and finely cut. Often the leaves and stems are easily torn or broken; since they are viviparous, this brittleness permits the plants’ proliferation in a wide area, especially in large earthen ponds. These plants can quickly overrun an earth-bottom pond.
Roots of underwater plants are often long and fibrous, serving both to anchor the plant and to draw nutrients from the soil. The exception is hornwort, which has no roots to speak of but instead floats in the water and absorbs nutrients through its foliage.Many underwater plants that root in the soil produce subsoil runners from which new plantlets quickly sprout. These plants, such as Vallisneria and Sagittaria, are able to form a carpet on the pond floor that holds soil in place, much like a sod. Potamogetons, myriophyllums, and hydrillas can form thick, branching mats anchored to the pond bottom that smother everything under them.
Greg Speichert & Sue Speichert "ENCYCLOPEDIA OF WATER GARDEN PLANTS" page 341-342