When I first put in our elevated pools--one to be a fountain, the other, a quiet pond for water plants--I tried every aquatic and bog plant I could lay my hands on. A few years later, I had discarded most and settled on just a few of the “floaters.”
These nautical types include the showy water lilies, water snowflakes and poppies, plus such oddities as water lettuce, water ferns and hyacinths that actually sail across the surface. Serenely floating on the silvery surface of the water, these floaters are the most satisfying and turned out to be the easiest to grow and control.
Many aquatic plants are rampant spreaders. A single water iris, for instance, grew to fill more than a third of my 3-by-11 1/2-foot pool in one year. There’s not much point having water in the garden if you can’t see it sparkling between the plants.
Floaters are better behaved, even though a few spread quickly. Water hyacinth, for example, can cover a pool in a day, or so it seems, but it is easy to pull out and toss in the compost pile.
Floating aquatics will even grow in a big container filled with water. Before building my ponds, I grew these same plants in half-whiskey barrels and huge pots with their drainage holes plugged.
Container-bound water gardens should be about 18 inches deep and 2 feet across for lilies; some of the other floaters can get by in less. Inside these big pots, put the plants in smaller containers filled with soil, which is also the best way to grow them in a pond or pool.
People ask if there are filters or pumps in my pool and if you have to change the water often. No filters or pumps are required, and you should never change the water. All you need to do is add water as it evaporates.
Filters and pumps are required only if you crowd a pool with fancy koi. Fish are necessary for the pond’s ecology, but ordinary feeder goldfish or mosquito fish do just fine without aeration. The fish take care of mosquitoes and, along with water snails, eat most of the algae. Fish you must buy, but the snails usually come with the plants (they don’t eat living plants, just algae or decaying leaves).
Changing the water upsets the balance, and you’ll get lots of algae; needless to say, never add chlorine to the water. Aquatic plants, especially the floaters, need still, quiet water, which is why my fountain, though it merely burbles, is in a separate pool.
If there’s a secret to water gardening, it’s to keep about 75% of the surface covered with plants so they shade the water. That keeps algae in check, although there is usually a period in early spring when green water can’t be avoided. Once the plants are all leafed out, they cover the surface, and the algae goes away.
In my pool, water lilies--three kinds of so-called “hardy” lilies and one tropical--are the stars. They start blooming in April and don’t quit until November. The star-like flowers are big, dramatic and brightly colored. Although each lasts only a day or two, one follows another so they seem always in bloom.
To add a little variety, I also grow the lily-like water poppies (Hydrocleys nymphoides), water hawthorne (Aponogeton distachyus) and the delicate yellow snowflake (Nymphoides geminata).
The yellow snowflake has fascinatingly frilly flowers and lily-like leaves marbled with brown and green--a nice contrast to the green-tinged-red lily pads. The snowflake sends out long runners that make more leaves and flowers, so it tends to pop up between the lily pads.
Water poppies spread in a similar fashion, with smaller green leaves and pastel yellow flowers that resemble California poppies.
The hawthorne has elongated leaves and garlands of white flowers that bloom mostly in winter, when the rest of the pool is nearly dormant. Flowers turn into little plantlets that root and become new plants.
All of these float like lilies with roots anchored in soil about a foot under the surface. They are planted in their own pots filled with the poorest soil from my garden.
Aquatic plants that require soil need a heavy, bog-like clay to grow in. Never use regular potting mixes and add only fertilizer to the soil you dig from your garden.
I grow my lilies in tubs about 10 inches deep by 16 inches across (in a pool that is 18 inches deep). A lot of people use plastic washtubs found at markets and hardware stores. The other lily-like aquatics can grow in one-gallon nursery cans. Drainage holes aren’t required when gardening under water, so if there are any, block them from the inside with strips of newspaper so the soil doesn’t leak out.
I usually add about an inch of soil, then a layer of aquatic plant fertilizer, then the rest of the soil and the plant. Get the plants and pots soaking wet, then put them in the pond. They’ll make the water murky for about a day.
Most of these plants, including the lavender-blue tropical lilies, can grow for several years in their original containers, but the yellow and pink hardy lilies grow so fast in Southern California that they must be repotted each March.
This is a big job because the containers are heavy, and you need to find a place to dump the old, mucky soil (watch out, this black muck stains everything it drips on). Cut off all but about four inches of the growing end of the lily tuber and replant horizontally so the top is above the soil. Put it to one side of the container so it has room to grow. In mid-summer, push special aquatic fertilizer tablets into the soil to keep plants blooming into fall.
The tropical lilies and other lily-like plants need to be repotted only every few years; repot them like any other plant, except for the need for clay garden soil.
To keep the pool planting from becoming too one-dimensional, I grow parrot’s feather (Myriophyllum aquatica), a filmy foil for the large round leaves of the other floaters. It’s planted in a container, but it spreads well beyond, simply dangling its roots in the water.
Another floater requiring no soil is the tiny mosquito fern (Azolla). Somebody gave me a few once, and they quickly spread to cover the whole pool, which was too much of a good thing. Now I keep scooping them out so that only a few clumps remain to float among the lilies.
Resembling leaf lettuce, water lettuce (Pistia stratoides) floats freely with inflated sponge-like leaves.
Aquatic plants can be a challenge to find. There also are several water plant specialists in Southern California, including Van Ness in Upland, which also sells mail order; Sunland Water Gardens in Sunland; McDonald’s Aquatic Nursery in Reseda, and Laguna Koi Ponds in Laguna Beach.