Choose a container that's at least 6 inches deep, with a dark interior and no drainage hole, or a half barrel with a plastic liner. (Dark colors discourage algae growth and camouflage it when it occurs.) If you want to use a terra-cotta pot, you'll need to glaze the inside to prevent water from evaporating rapidly.
You can pick from many kinds of water garden plants. Small plants should be potted in a clay-type potting mix (not a commercial potting soil, or any soil with fertilizer). Some plants merely float on top of the water. Use a tablet fertilizer for blooming plants.
To keep the soil in the pots anchored, scatter pea gravel over the top of the soil. Fill the tub with water and set your plants in place.
A half inch to an inch of water always should cover the base of the plants (up to several inches for water lilies). To prop them to their appropriate levels in the water use bricks or dark-colored stones. Add water as needed to compensate for daily evaporation.
A water garden needs full sun for at least six hours per day. Choose plants with a variety of leaf shapes, heights and colors, so the container always looks attractive.
To prevent breeding mosquitoes, buy dunk tablets at a garden center and follow directions. Don't use water drawn from a softener. If your water contains chlorine, before planting let the water sit for 24 to 48 hours, so the chemical evaporates. If your water contains chloramine, you can buy products at garden centers to remove the substance.
1. Water hyacinth (shown not in bloom)
2. Curly mint (Mentha aquatica var crispa)
3. Lizard tail (Saururus cernuus)
4. Dwarf papyrus (Cyperus profiler) 'Nanus'
5. Taro (Colocasia esculenta) 'Illustris'
6. Siberian iris
7. Water lettuce
8. Houttuynia 'Chameleon'
Some of the floating plants in a water garden such as water lettuce and water hyacinth will multiply and crowd across the surface of a container throughout the season. When that happens, just lift up the plants and separate them, keeping the ones you want. Maintain about 40 to 50 percent of open water surface. Discard the excess plants, create a new container or give them to friends.