Gardening Articles: Flowers :: Annuals
Making a Water Garden in a Tub
by Ann Whitman
To the uninitiated, water gardens seem complicated, expensive, and fussy. But they don't have to be, especially if you start small with a water garden in a container. Many of the principles of gardening in water are the same as those for gardening in soil. If you can grow a tomato, you can grow a water lily.
Ornamental and Edible Plants
In your garden, you probably have shrubs, some flowering plants and vegetables, and a lawn. Think of water plants in the same way. Tall bog or border plants, such as marsh marigold (Caltha palustris), canna, sedge (Carex), taro (Colocasia esculenta), and cat tail (Typha), grow with their roots submerged and foliage above the water. As with shrubs in a terrestrial garden, their size and height add structure and provide a backdrop for flowering plants.
Submerged or oxygenating plants, such as fan wort (Cabomba), anacharis (Elodia or Eyeria), parrot's feather (Myriophyllum), and eel grass (Vallisneria), live underwater where they supply oxygen and compete with algae for nutrients. Floating plants like duckweed (Lemna) and water lettuce (Pistia) move freely across the water surface and provide algae-suppressing shade. Like turf grasses or mulch, they are not the stars of the show but are necessary to the landscape.
Keep in mind that some aquatic plants can be invasive and are prohibited in certain regions. Water lettuce and water spinach (Ipomoea aquatica) are prohibited in some states, including Texas, Florida, and South Carolina, and it is illegal to possess water hyacinth (Eichhornia) in many states. Though most mail-order companies will not ship to these areas, it is best to check with your cooperative extension office before ordering.
When you think of ornamental water gardens, exotic-looking water lily (Nymphaea) and lotus (Nelumbo) blooms and intriguing foliage probably first come to mind. Sedges, grasses, Japanese iris, and scores of other plants also add beauty.
Aquatic vegetables are less familiar in this culture, but they are dietary staples in many others. Aquatic crops that are well suited to small water gardens include taro, Chinese water chestnut (Eleocharis tuberosa), arrowhead (Sagittaria latifolia), and cat tail. (For others, see "Edible Water Plants" below.)
Pots and Soil
Most water plants grow in pots. Nursery pots like the ones perennials are sold in work well, or you can buy planting baskets made for water gardening. Line the pot or basket with two layers of newspaper to keep the soil from sifting out. In general, dwarf water lilies and submerged plants need pots about 6 inches in diameter and 6 inches deep. Most bog plants, full-sized lilies, and dwarf lotuses need pots at least 12 inches across and 6 inches deep. (Planting these in deeper pots is fine but not essential.)
Water plants need heavy, humus-rich soil like fertile garden soil or a good commercial topsoil or a water plant mix. Never use a potting soil that contains peat, perlite, or vermiculite because these ingredients float. After you pot your plant, cover the soil surface with a 1/2- to 1-inch layer of rinsed gravel to prevent fish from stirring up the soil.