Aquatic plants aren't just used in the water garden to provide beauty and naturalization - they also serve the very important function of helping to balance the pond ecosystem. Their valuable biological filtration helps remove nitrogen, ammonia, nitrates, and other minerals that algae would otherwise feed on. In addition, the plants provide food, shade, and protection for the fish and wildlife that live in and around the pond. Typically, they are divided into four groups - water lilies, marginals, floating plants, and submerged plants.
Water lilies are available in hardy and tropical varieties. They both come in a wide variety of colors, shapes, and sizes and the leaves provide fish with shade from the heat of the summer sun, cooling the water and making algae control easier too.
Hardy water lilies are reliably perennial from the northern reaches of Zone 3, to the subtropical areas of Zone 11. The white, pink, red, or yellow flowers float directly on the water surface and are open during the day. When cold weather comes, the foliage dies. This should be removed before winter. New leaves emerge again in the spring.
The flowers of tropical water lilies sit above the water and come in the typical whites, yellows, pinks, and reds. Unique to tropical water lilies are the blue shades - light blue to deep purple. Flowers are also more often fragrant and there are varieties available that bloom at night.
Although tropical lilies are only hardy to zones 10 and 11, they can be planted in colder zones when the water temperature is consistently above 70? F and treated as annuals or over-wintered, if given proper care.
Marginal aquatics are the plants found growing around the edges (margins) of a water garden. They add valuable filtration to the pond and they remove elements that would otherwise feed algae.
To create a natural-looking pond, a good selection of marginal plants is very important. There are hundreds of varieties - hardy and tropical - that come in all shapes, sizes, textures, and flower colors.
How to Plant Marginals
In a rock and gravel pond, marginal plants are generally placed directly into the gravel. This allows them to thrive naturally, and filter the water more effectively. Invasive species should be kept in pots that are buried in the rocks and gravel. Well-behaved plants can be taken out of the pots and planted directly in the gravel where the roots can absorb nutrients directly from the substrate of the pond where fish waste and other organic debris settle and begin to decompose.
Choose the area you wish to place the plant, move the gravel aside with your hands, place the plant, and spread the gravel around the base to support the plant and hide the pot. If you're planting bare-root, remove the plant from the pot and wash away any loose soil before planting. Tropicals that you plan to bring indoors over the winter, should be left in the pots to make removal easier.
Floating aquatic plants float on the water surface while their roots hang down into the water. Most are tropical, but a few are hardy perennials in climates with hard winter freezes. These plants may be used to shade the water, helping with summer algae control.
Plants such as hyacinth and water lettuce do a great job of disguising the open top of the BIOFALLS® filter, while providing excellent filtration. Use a stick across the spillway to keep the waterfall from carrying the plants over and into the pond. They can also be floated in the pond, however care must be taken to make sure that they don't end up in the skimmer.
Submerged Aquatic Plants
Submerged plants are commonly referred to as oxygenators, but this is a false description. These plants do produce oxygen during the day, but at night and on cloudy days, the cycle is reversed and they use oxygen and produce carbon dioxide. These plants are still important allies in creating a well-balanced water feature by using nutrients in the water. They also provide great hiding places for baby fish.