Building a Water Garden

Choosing a site:

Determine your water garden’s function, and think about the contours of your land. A natural depression near your patio, for example, might suggest an informally shaped pool that would complement a nearby flower border. Consider likely reflections from all angles, and study possible views from the house, deck, and other parts of the garden. A water feature located close to your summer sitting area or well-used areas of your home will stretch your enjoyment throughout the seasons.

Think through what you want before you choose the location.

– Will you want plants that are ardent sun-worshipers?
– Do you want moving water?
– Is there electricity nearby so you can readily run a line for a pump?

Size depends on existing vegetation and the lay of the land as well as the water feature’s proportion to other elements in the landscape. The water’s surface area is only half the issue. You will be constructing a backdrop and side-drop of plant materials that will give it a much greater sense of depth.

You may come up with half a dozen equally good designs. Make sketches of different types and shapes of water features for the area you’ve chosen, and outline your ideas with a hose or string. If you don’t trust your design capabilities, call a nursery that does installations, and ask whether the staff designer can take a look at your plans. He or she may also be willing to do an on-site consultation for a small fee.

Site your little oasis in at least half-day sun, away from trees that shed heavily and other producers of falling fruit and seed pods: you’ll have to skim leaves from the water’s surface and fish out any debris. And, of course, you’ll need to make any necessary corrections so that sloped terrain doesn’t carry waves of silt into the pond during heavy rains.

Check with local authorities for any restrictions on the depth of unfenced water features. After digging the hole, make sure the area is free of rocks and sharp objects that could puncture the liner. Use sand beneath the rubber for extra padding so that you can work in the dry pond without puncturing it.

Selecting plants. Every water garden needs a balance of floating and submerged plants. Floaters vary according to planting depth and how much surface area of water they need. Roughly half a pond’s surface should be covered with plants. Submerged plants such as Washington grass (Cabomba caroliniana) and wild celery (Vallisneria americana) are invaluable as water filters.

Water lilies (Nymphaea). These luxuriant flowers are skirted by beautiful, broad-leaved, often mottled foliage that provides shade and cover for fish. Water lilies need calm water, and most require at least four to six hours of sun a day.

Blossoms of hardy varieties float on the surface, opening in the morning and closing by mid- to late afternoon. Cultivars come in white, pink, salmon, red and yellow, and fully double forms resemble peonies. Hardy water lilies can overwinter even in Zone 3 if the rootstock stays below the ice.

Tropical water lilies are grown as tender annuals in Zones 3-9 but can overwinter in Zones 10-11. Often heavily fragrant, the blossoms stand well above the surface of the water. Night-blooming tropicals open in the evening and close by midmorning; day bloomers usually open by midmorning and close by mid- to late afternoon. Tropicals bloom larger, brighter, and more profusely than hardy water lilies, and some come in nearly mystical shades of blue and lavender.

The delicate foliage of floaters such as the four-leaf water clover (Marsilea mutica) and floating fern (Ceratopteris pteridoides) add variety and texture to the water’s surface.

Lotus (Nelumbo). Symbol of the sacred for Hindus, this magnificent plant produces huge, fragrant blossoms in shades of pink, coral, white, red, yellow and muted combinations. The flowers bloom on stalks that soar from one to three feet above the water’s surface. The aerial leaves are round platters one to two feet across. Smaller varieties with relatively little spread are also available. This aggressive plant would soon take over an earth-bottom pond but does well in containers too. Lotuses perform well as far north as Zone 4, except in the Pacific Northwest and Alaska, where summer temperatures are too low for them to bloom.

Other marginal plants–those that need only two to 12 inches of water–include pickerel weed (Pontederia cordata), arum lily (Zantedeschia aethiopica), and white arrow arum (Peltandra alba).

Preserving your budget. A water garden needn’t break the bank. A 6- by 10-foot pond, including liner, pump, mechanical filter, plants and fish, needn’t cost you more than $700. You could spend a lot more, of course–cost increases with size–but you could also spend less.

Five steps to building a simple pond

Site your pond in a level, well-drained, sunny site away from shedding trees. Avoid low areas where puddling occurs or where erosion from higher elevations is possible. Dig the hole, sloping the edges to prevent cave-ins. Leave a shelf along the perimeter for marginal plants, or place them on upside-down pots or brick towers. Remove rocks, debris and roots.

To ensure that the water’s surface will be parallel to the plane of the pond, level the pond’s top edge by placing a board and a carpenter’s level across the hole. Correct any imbalances by leveling high spots, making sure that the rim remains higher than the surrounding terrain.

Add an inch of sand for cushioning on the bottom of the pond. To calculate liner size, add twice the pond’s depth, plus two feet for edging, to both the pond’s length and width. A 10- by 12-foot pond that’s two feet deep would thus require a 16- by 18-foot liner. Unfold the liner in the hole, and weight the edges temporarily with stones.

Fill with water. Trim the liner, leaving a 6- to 12-inch flap all the way around. Secure the liner by nailing the flap to the ground with six-inch nails. Edge the pond with rocks, bricks, or flat stones to conceal the flap and protect the liner from the sun’s ultraviolet rays.
Pot aquatic plants in heavy soil in pans or tubs and place in the pond; use sand for potting submerged plants.

Wait a week or two before adding fish, snails, or other creatures. Be patient through the first flush of algae, which usually begins soon after filling. When the submerged plants and water lilies become established, they’ll keep the algae in check. Now sit back and enjoy.