By Robert Smaus

Many people think that water gardening is difficult. Water gardens look so exotic. But nothing could be further from the truth: I would recommend water gardening to a rank beginner, although I might think twice before suggesting growing something as common as roses.

If you follow a few simple rules, it's fall-down easy. The rules may seem odd because all sorts of garden wisdom gets turned upside down when you're gardening in water. For instance, forget fast-draining soil mixes. Pot things up in the heaviest clay soil you can find.

The Four Rules of Water Gardening

Pond gardening is easy but there are four very rules to remember. They are: Ponds need aquatic plants, fish, and water snails for ecological balance; Grow aquatic plants in their own pots, in ordinary garden soil; Keep 75 percent of the water surface covered with vegetation; and You should never need to change the water.

The Main Ingredients

You need a pond or container, water, aquatic snails, fish, and plants. What about expensive things like pumps and filters? Water gardening isn't like keeping tropical fish. You don't have to change the water. After all, you never change the water in a natural pond. Just restore what evaporates, and the garden won't require pumps or filters unless you're trying to keep koi, those fancy Asian carp.

Creating a water garden doesn't take much; an old half-barrel or a big pot with a plugged drainage hole enlivens the smallest garden. I've seen ceramic containers about the size of a 5-gallon nursery pot filled with only floating mosquito ferns-also called azolla (Azolla filiculoides) add sparkle to the smallest balcony garden. And water gardens are irresistible. Even the tiniest one will draw children and adults to peer into its mysterious depths. Some gardens, mine included, are designed with a water garden as a central feature.

Two Kinds of Water Gardens

Water gardens are either still or active. You can garden in the first type but not the other. Fountains and cataracts add sparkle and splash to a garden, being noisy and full of flash. Some fountains don't disturb the water significantly, and lilies can live in water gardens with them if the splashing isn't contant, or if they are located away from the fountain. Most aquatic plants prefer calm water, with the exception of watercress, which seems to prefer moving water. Quiet pools also have their own romance. They reflect the sky and ripple in the slightest breeze. I built one of each type side-by-side in my garden.

Types of Aquatic Plantings

I've tried just about all available aquatic plants in the larger pool but have settled on what I call "floaters". Aquatic plants grow faster than anything else, and most types will soon choke your pool. Water lilies, which bloom in my garden from spring to winter, and a few other aquatics with floating leaves, seem the easiest types to control. Even the deceptively delicate water irises spread so quickly that after a year they occupied almost half my pool, though some kinds are slower spreaders. Aquatics with floating leaves, water lilies included, also need yearly attention. Repotting is a major project with the hardy lilies. In artificial pools, grow aquatic plants in submerged containers so they can be lifted out and maintained. However, heaving a plastic pot filled with soggy soil is tricky-and messy, too.

Building a Water Garden

Depth. The ideal depth is about 18 inches. In many communities, that's also the legal depth. Any deeper, and some building codes consider it a swimming pool, which might mean that it must be fenced and that you'll need a permit to build it.

An aboveground water garden can be shallower than 18 inches. For years, I used half whiskey barrels, after carefully swelling the slats shut by filling and refilling the barrel halves with water. I then graduated to 2 1/2-foot-wide concrete pots with plugged drainage holes, but the pots were only about a foot deep, the minimum for many aquatics. I managed to grow small water lilies and other aquatics and keep a few goldfish.

My current pool is 18 inches deep but above the ground, so visitors can sit along its edge.

Lining. You can also excavate an inground pool and use a special pond liner made of polyvinyl chloride (PVC) or ethylene propylene diene monomer (EP rubber). Or, build a pond out of materials such as railroad ties, and line the inside. Some nurseries stock liners and preformed ponds that you simply bury. Or, you can order materials by mail.

Planting a Water Garden

Where to find plants. Once you have the pond, shop for plants. Many nurseries carry them only in the summer, but many mail-order sources are also available. Suppliers' catalogs have information about installing a garden, pond-making supplies, snails, and plants. However, if you know someone with a water garden, you can probably get all of your plants free. They multiply quickly, and every spring, gardeners compost many divisions.

Containers. Most aquatics grow best when planted in wide, shallow containers that you submerge in the pond. I use old plastic nursery cans and cheap plastic washtubs. Water lilies' containers must be about 18 inches wide and 10 inches deep. Plants with shorter stems and smaller root systems can grow in smaller containers. Unlike aboveground containers, these pots don't need drainage holes. If the pots have any, cover them with two layers of newspaper so soil doesn't leak out. (Newspaper takes years to decompose under water; even pulp pots last a long time, like the timbers of a sunken ship.)

Soil. Forget what you've learned about potting soils. Avoid regular potting mixes and soil amendments. They contain elements that will rot, pollute, or float. Aquatics grow best in containers filled with ordinary garden soil. The heavy clay garden soil that you regularly curse over is fine for aquatic plants. Dig some up, and break up clods to use it as aquatic potting soil.

Some people cover the soil with sand or pebbles to keep it from muddying the water and to prevent fish like koi from digging up the plants. I don't. After planting, I simply soak the soil in the container and then set the container in the pool. It's heavy enough not to float, and the water clears in about a day.

Fertilizer. At planting time, add a little aquatic-plant fertilizer, especially for lilies. Cover the fertilizer with soil, or it will escape and feed the pond's algae. I use tablets made for aquatic plants, and place them next to the roots.

Stocking the Water Garden

Fish control algae and mosquito larvae. Ordinary goldfish control both, though tiny, guppylike mosquito fish eliminate mosquitoes completely. (Mosquito-control agencies often give these fish away.) My first goldfish came from an elementary-school carnival where my kids won them by tossing little white balls into cups filled with the hapless fish. Pet stores sell them, often as "feeder fish" for snakes and other reptiles (imagine your fishes' delight when they find themselves in a water garden instead!). If you like aquatic plants, don't keep koi in the same pond. They'll eat everything (though lilies usually survive).

Pest Note: If your neighborhood includes raccoons, they're likely to climb into the pond, dig things up, and try to eat the goldfish. In this case, the less attractive mosquito fish are better bets than goldfish. To keep raccoons out, you must install a single-wire electric fence, which greatly detracts from the pond's beauty. However, not much else deters them.

Aquatic Snails. Water snails don't eat living plants, just decaying vegetation and algae. Many garden rules are reversed when you start water gardening: You don't want good drainage; instead, you use crummy soil, and you actually encourage snails.

Keep about 75 percent of the water's surface covered with vegetation in the summer to inhibit algae growth. Algae are a natural part of pond life, and some forms always coat the pond lining. Some shade minimizes algae. They cover my pool's sides, but the water stays clear. Annually, after I repot the aquatic plants, the pool briefly turns green as the algae eat stirred-up nutrients. That's why you must never change the water. If you do, the pond must achieve its natural bal all over again.

Some Favorite Aquatic Plants

In my garden, water lilies (Nymphaea) start blooming when the weather warms and last long into the fall. Their starlike flowers are bright and magical as they float serenely on the water's surface. I grow tropical and hardy water lilies.

Tropical Water Lilies

Most flowers are lavender, purple, or fluorescent pink. Some bloom at night. Most tropical lilies spread widely. Small ones are available; my favorite is 'Edward D. Uber', with purple flowers. In my garden, this variety stays in the pool all year. I repot them only every few years because they don't spread like the hardy lilies, though they bloom just as profusely. Where winters are cold, treat tropicals as annuals.

Hardy Water Lilies

These plants are hardy from USDA Hardiness Zones 3 to 11, but whether you must move them indoors depends on the pond or container they're planted in and the extremes of cold in your area. In very cold-winter regions, you must take in hardy lilies growing in small tubs; store them in a garage or basement.

In milder cold regions, a de-icer that you float in the water and plug into an electric outlet will keep the water from freezing. You must take in lilies grown in containers in small inground water gardens also. Cover them with wet newspaper to keep them moist while dormant.

These lilies survive in natural outdoor ponds if the crowns and rhizomes are not in frozen earth under the ice in winter. The flowers, stems, and leaves die back, but the rhizomes remain alive. Find out the extreme maximum ice depth in your area. If your pond is deeper than that, your plants are probably safe. If you're not sure, take them in.

These lilies come in wonderful shades of pink, white, red, and yellow. During a season, the tuber will creep from one side of the pot to the other and, if the pot is too small, grow right over the edge. To contain them, repot when the weather warms in spring.

Hardy water lilies must be repotted every spring in a process that's similar to potting them up initially. With a serrated knife, saw off several inches of the growing end (the end with the leaves). Also, trim back roots so you end up with a block of root-filled soil about 8 inches square. The old soil will have turned jet black. It stains everything, so quickly wash spills off paving and other surfaces.

In a container wide enough to allow room for the roots to spread, plug any drainage holes with two layers of newspaper. Then plant the chunk of roots and leaves in ordinary garden soil at one edge of the container so that it can grow across the container. All water lilies need fertilizer at planting time and later in the season. Little tablets specifically for aquatic plants are the easiest to work with if you follow label directions.

After water lilies, my favorite additions to the water garden are (in order of preference):

Yellow snowflake (Nymphoides cristatum). Flowers on this aquatic plant are frilled like a snowflake. Its leaves are like a lily's but extensively marbled with green and burgundy. It's considered hardy from zones 6 to 10. In cold-winter areas, protect it as you would tropicals.

Water poppy (Hydrocleys nymphoides). This aquatic also has floating leaves, and it's adorned with clear yellow poppy flowers. North of zone 8, it's grown as an annual. Though quite hardy in my garden, it nearly disappears during the winter, like most aquatics.

Water hawthorn, also called Cape pondweed (Aponogeton distachyus). In my zone 10 climate, this aquatic takes the water poppy's place in winter. Its floating leaves are long and narrow. The white vanilla-scented flowers are floating racemes (flower spikes) that bloom in winter. The whole plant vanishes below water in summer and reappears in autumn. In cold climates, this plant blooms only in summer.

Parrot's feather (Myriophyllum aquatica). This reasonably well-behaved aquatic has feathery green foliage that floats on the surface between the lilies in my pond. The "feathers" stand about 6 inches above the water and add vertical form to the pond. If I let them, they would take over, so I hack away at them through the season.

Floating Plants. All of the above aquatic plants grow with roots submerged and tops floating on the water, but some aquatics actually float, roots and all, like little boats. You could call these "nautical" plants. The lavender-blue-flowered water hyacinth (Eichornia crassipes) is the best known but is far too weedy in my zone, quickly forming an armada. I like the gray-green leaves of water lettuce (Pistia stratiodes), another boatlike floater, and the tiny fronds of Azolla filiculoides, a fern that happens to float.

Submerged Plants. A few plants, called oxygenators, grow completely submerged. Supposedly they add oxygen to the water for the fish but actually they absorb extra nutrients that might increase algae levels. I grow only the fluffy fanwort (Cabomba caroliniana), and must remove lots of it every few weeks because it grows very fast.

Bog Denizens. Bog plants grow with their roots just under the water's surface. I've planted water irises, azure pickerel weed (Pontederia cordata), and the tall and stately red-stemmed thalia (Thalia dealbata). I have even added cannas, which do better in the pond than they do in my garden. All have quickly overgrown, so now I stick to the well-behaved water lilies and their friends.

Robert Smaus is the garden editor of the Los Angeles Times and has been the West Coast host of PBS's "Victory Garden."

Photo by NGA member "pmenefee".

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