Posted by Brent Wilson on 8/27/2016 to Container Gardening
Gardening with aquatics is similar to other forms of gardening in that you have to be aware of proper soil conditions, kinds of containers, proper planting techniques, fertility needs, and after planting care. What makes water gardening unique is that the plants you grow will be growing with their roots under water. Water depth, water temperature and what to do with plants during the winter are things you'll have to consider.
Soils for Aquatic Plants
Aquatic plants, such as water lilies and lotus do best when they are planted in heavy clay loam soils similar to what you would have in a garden setting. Commercial potting mixes are too lightweight and do not hold nutrients for any length of time so not good for use when planting aquatic plants.
Containers For Aquatic Plants
Choose containers based on the size of your garden pond, and the purpose. The size of the pond dictates the size of the container and the types of plants that you will grow. Containers that are about 15-18 inches in diameter and 10 inches deep are suitable for hardy water lilies. Tropical water lilies prefer a little larger container: 20 inches in diameter and 10 inches deep. For other types of plants, containers in the range of 6 to 20 inches are suitable. Keep in mind that larger containers will allow plants to grow larger, and smaller containers tend to grow smaller plants.
Planting Instructions for Aquatic Plants
Use damp, average garden soil for planting aquatic plants. Fill the container about two-thirds full of soil.
Hardy Water Lilies: For hardy water lilies, the rhizome should be placed to the side of the pot, and faced at an angle to grow toward the center of the pot. Look for buds, or "eyes", to determine which end is the growing point. After the rhizome is in place, cover it with soil so that the growing point is just slightly above soil level.
Tropical Water Lilies: Plant tropical water lilies in the center of the pot with the growing point slightly above the soil level.
Lotus: Plant Lotus at the center of the pot. Lotus rhizomes are very brittle so handle them carefully during the planting process. Plant Lotus rhizomes in large containers covering them with about 2-4 inches of soil with the growing tips above the soil level.
Emergent and Submerged Plants: Potting emergent and submerged plants is similar to planting other aquatics. Place some soil in the pot. Center the plant and add soil to cover the roots. Or, you can fill the container with very wet soil and then gently press the roots into the soil.
Once planted, the soil should be covered with a 1/2 inch layer of pea gravel, or some type of small stone. This will help prevent soil from escaping and clouding up the water, and discourage fish from digging.
After planting, water thoroughly and then slowly lower the containers into the pond at the proper depth.
Placing Plants in the Pond
Hardy Water Lilies: Submerge hardy water lilies to a depth where 12-18 inches of water will be above the top of the pot. If the pond is in full sun, the minimum amount of water over the top of the pot should be from 6-8 inches for the plant to grow well. If the pond receives less than 6 hours of sun a day, then 6 inches of water above the top of the pot is sufficient for the plant to get the sunlight it needs.
Tropical Water Lilies: Submerge tropical water lilies to a depth of 6 to 12". They grow best at 12".
Lotus: Grow lotus in the pond with 4-6 inches of water over the top of the pot.
Emergent Plants: Most emergent water plants, such as Iris, can be grown with the top edge of the pot at water surface level, or with 2-4 inches of water over the top of them.
Bricks and inverted pots work well to adjust the height of planted pots in the pond.
Timing the Placement of Plants in the Pond
Hardy water lilies, lotus and emergent plants are tolerant of cooler water temperatures and can be placed in the pond when temperatures reach about 50 degrees F. Tropical water lilies and some of the floaters cannot tolerate cold temperatures so should be placed in the pond when temperatures are above 70 degrees F.