Water gardening requires proper planting conditions, just like any other kind of gardening. You need to be sure to have the correct soil, a good location, and quality plants. But there are special considerations for water gardens that are different from traditional types of gardens.
You’ll have to deal with considerations such as the depth of the water, the temperature of the water, and how to keep your plants and animals safe during the winter. Most aquatic plants seem to do better in a heavy, loamy, clay-based soil.
You can’t use standard potting mixes, because they are far too light, and they won’t hold on to nutrients for very long. The soil you plant your aquatics in should be damp. You’ll fill your container about 2/3 full of the soil.
Water lilies should have their rhizomes placed so the growing tip is pointed to the center at a bit of an angle. The growing tip usually has eyes, a bit like a potato. This way, it can grow across the center of the container.
After you have the rhizome place properly, you’ll cover it with soil so the tip is just slightly above the soil level. The exception is tropical water lilies, which are planted in the center of the container.
Lotuses are also planted in the center, but their rhizomes are very delicate and should be handled carefully. Emergent and submerged plants should be potted by putting some soil into a pot, centering the plant in the pot, and covering its roots with more soil.
Once they’ve been potted, you need to cover the soil with about ½ inch of small gravel. This helps keep the soil from clouding the water and also from eroding away. Once you’ve properly potted your plants, they should be submerged to the correct depth.
You can place bricks underneath containers to help bring them to the correct depth. Check the planting instructions for each plant to see what level the plants should be submerged to. Water lilies generally grow best at a depth of about 12 to 18 inches above the top of their container.
The pot could be placed at a shallower depth at first, and lowered later as the plant grows. The more sun the pond gets, the deeper the container can be placed in the water. Tropical water lilies need to be at 12 inches depth if possible, but they can grow in only 6 to 8 inches if they have to.
Lotus plants only need about 4 to 6 inches of water over the top, and emergent plants generally only need a couple of inches of water over them. You can adjust the height of the various plants by placing bricks or inverted pots underneath.
Be careful not to over-fertilize your water garden. This can lead to an algae problem. You can use slow release tablets or some sort of granular fertilizer. Several different types would be acceptable, including 5-10-5, 12-8-8, 10-6-4, and 20-10-5.
You should fertilize every month from spring until August. Tablet fertilizer is generally the easiest to use. You simply have to push the tablets into the soil. Most aquatic plants won’t do very well in cold weather, so they need to be over-wintered.
This means you’ll need to take some precautions to ensure your plants aren’t killed by ice and freezing temperatures. For very shallow ponds, this will mean the plants need to be brought indoors for the winter.
They need to be kept above freezing, but below 50 degrees so they stay dormant. Be sure to keep the roots very moist at all times until spring. You can also remove rhizomes from their containers and store the plants in moist sphagnum moss inside plastic bags. Tropical water lilies must be stored in an aquarium tank with a lot of light at about 68 degrees.