Most aquatic plants require at least 5 hours of direct sunlight to grow well so keep this in mind when you decide where to build your pond or place your containerized water garden.
Planting in Containers
Water plants tend to be vigorous and should be planted in plastic containers without drainage holes or in special fabric pots made for water plants to prevent spreading and overcrowding. Plastic baskets are also available.
Fill the containers with heavy garden soil that is free of chemicals and fertilizers. After placing the plant in the container, pack the soil tightly in the container leaving 1-2 inches of space below the container rim. Cover the remaining depth with pea gravel or sand to keep the soil from floating up. The exception to this is water lilies: do not cover the growing point of water lilies with soil or gravel. You can still put pea gravel in the pot but keep it away from the growing point.
Fertilize container grown plants with slow release tablets placed in the container at recommended rates. Floating plants are generally fertilized with liquid or water soluble fertilizers specifically manufactured for aquatic plants. Follow label directions closely since over fertilizing can cause too much algae growth.
Marginal plants should be planted in individual 10- to 12-inch plastic pots. Plant in heavy garden soil, covering the top with pea gravel or sand. Fertilize according to label directions. Marginal plants should be lowered to a depth of only 1-6 inches. They grow out of the water and are usually found at the water's edge.
These plants don't have to be planted. Simply place them in the water and they will grow. Many floating plants are tropical and cannot tolerate a frost.
Rooted Floaters (except water lilies)
These plants grow like water lilies do: their roots grow in pots several inches under the water but the foliage floats on the surface. Use 1-gallon containers filled with heavy garden soil, covering the top with pea gravel or sand. Fertilize according to label directions. Lower the container to 6 to 12 inches of water over the top of the pot. Some of these are hardy and can be left in the pond through winter; others are tropical and must be placed in a heated greenhouse for the winter.
All ponds should have submerged plants to help maintain clean, pure water. These plants deter algae growth by using processing excess nitrogen and putting oxygen into the water. Plant submerged plants in one gallon containers in heavy soil with pea gravel to hold them in place. Completely submerge the top of the pot to a depth of at least 12 inches.
Hardy Water Lilies
Hardy water lilies bloom from June through September depending on the weather, and become dormant during the colder months. These lilies can be left in a pond year round. As spring approaches, growth begins again.
Most hardy lilies have flowers that float on the water surface or rise slightly above it. Some are fragrant and others are not.
For the average to large size water lily, a five to seven gallon container is ideal. Small water lilies can be potted in a three to five gallon container. Hardy water lilies grow horizontally across the container so a wide pot is best. Special water lily baskets are also available. The rhizome should be planted horizontally with the crown or growing tip at one edge of the container. Do not cover the growing tip with soil or pea gravel. Top with an inch or two of pea gravel or sand. The container can be lowered to a depth of 6 inches to begin with, and then lowered to a depth of 12 � 18 inches as the plant grows. Hardy lilies should be planted in early spring and fertilized according to label directions.
Dividing and Repotting Hardy Water Lilies
Hardy water lilies should be divided every two or three years depending on the size container plants are in. For the average to large water lily, a five to seven gallon container is ideal. The best container will be shallow and wide. Small water lilies can be potted in three to five gallon containers.
Begin by removing the soil from the water lily using a water hose to expose the rhizomes. Select the best looking piece with good growth and cut to about three inches long, discard the remainder of the plant. Trim away excess roots and damaged foliage. If the water lily is to remain unpotted for any length of time, keep it in the shade with damp paper towels or newspaper covering the plant.
Mound soil against one side of the container and place the rhizome at a 45 degree angle with the cut edge against the pot and the growing point at the level the top of the soil will be. Add more soil to within a couple of inches of the top of the container. Firm the soil in place and add about one inch of pea gravel to cover the soil but keep it from covering the growing point of the plant. Gently add some water to the container and then slowly lower the plant into the pond.
If you place the plant just a few inches under the water for the first few weeks, you will get faster growth. After this, place the plant at the proper growing depth of 12 - 18 inches of water over the top of the plant and fertilize.
Lotus are hardy plants that can be left in the pond through the winter. Lotus come in several sizes from dwarf types that will grow in a two or three gallon container to the standards which are better off in a 20 to 30 gallon container. Standard lotus planted in small containers do not bloom well. Be careful handling lotus so the growing point is not damaged. If the growing point is broken the plant is likely to die. Water that is too cold when the lotus is put in the pond can also kill the plant.
Fill the container with garden soil and place the tuber with the cut portion against the edge of the pot. Add more soil and pea gravel but do not cover the growing point. Cover only with a couple of inches of water until the plant is growing well and then it can be lowered to the point where it has several inches of water over the top of the pot. After the lotus are well established, fertilize according to label directions.
Tropical Water Lilies
Tropical water lilies bloom profusely with very fragrant that grow well above the water�s surface. Some are day blooming and some are night bloomers.
Tropical water lilies cannot tolerate cold temperatures and should not be planted until the water temperature reaches at least 70 degrees F. Day time temperatures of 75 degrees F and night time temperatures of 65 degree F are best. Planting too early can cause dormancy and restrict potential growth of the plant.
For the average to large size water lily, a five to seven gallon container is ideal. Small water lilies can be potted in a three to five gallon container. While hardy lilies grow vertically from a rhizome and should be planted at a 45 degree angle, tropical water lilies grow vertically from a crown so should be planted upright in the center of the pot. Fill the container with heavy garden soil then firm the soil around the roots but leave the crown (where the stems and roots connect) level with the soil line Top with an inch or two of pea gravel or sand but do not cover the growing tip with soil or pea gravel. The container can be lowered to a depth of 6 inches to begin with, and then lowered to a depth of 12 - 18 inches as the plant grows. Fertilize according to label directions
Overwintering Tropical Plants
Tropical plants are not likely to overwinter and need to be replaced every spring or taken into a greenhouse pond for protection when it gets cold. Most containerized aquatic plants should be divided and repotted every three to four years.