As anyone who has snorkeled can attest, the cool aquamarine light underwater casts an enchanted glow on everything in its domain. Perhaps this explains the allure of water gardens. Small freshwater gardens are fun to create and simple to care for. And all you need are a few floating or submerged greens in a vintage aquarium, an apothecary jar, or a sleek glass cylinder. You'll find appropriate containers at antiques shops, garden centers, or in your own cupboards. Aquarium suppliers and specialty nurseries sell a variety of suitable plants.
Those that can remain entirely submerged in water, such as anubias and parrot's feather (Myriophyllum), are known as true aquatics. Semiaquatics, such as sweet flag (Acorus americanus) and umbrella palm (Cyperus papyrus), like to have their roots submerged and their foliage above the surface. Floaters, such as water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes), drift freely on the water's surface. A few plants, including dwarf arrowhead (Sagittaria natans) and parrot's feather, are so adept at converting carbon dioxide into oxygen that they are referred to as oxygenators. They help to keep water free of algae, which can loud the water and kill the plants. You can use any of these-singly or together-in a water garden.
When choosing plants, keep in mind that some will need twelve hours or more of bright light daily. Place these beneath fluorescent grow lights from an aquarium supplier. Avoid using incandescent lights, which can overheat the water and burn foliage. A few species, including sweet flag and arrowhead, can survive on a bright windowsill. Some water-garden favorites, including lace plant (Aponogeton) and sword plant (Echinodorus tenellus), have difficulty setting down roots in soil; place them in gravel or in other loose substrates available at aquarium suppliers.
Rinse gravel thoroughly to remove dust, which can cloud the water, and salt, which can damage roots and leaves. Spread the substrate in the bottom of the water garden before adding ordinary tap water. You should first leave the water in an open container for at least one day, though, to let any chemicals evaporate. With the water garden half full, place plants directly in the gravel. Make sure their crowns are not covered; this will impair growth. The crowns of marginals should be slightly above the surface of the water when the container is filled.
A few plants, such as black taro (Colocasia) and bamboo plant (Calamus), may be sold potted in plastic containers. Place these on the bottom of the container, and use gravel to cover the surface of the pots. This keeps the soil in place when you add more water. You can hide the pots beneath decorative stones. Because these plants tend to be large, they are suitable only for ample aquariums (at least twenty-gallon) or deep, oversize vessels. Fill the tank with water; use stones to anchor plants that pull free of the bottom. Place floating plants last.
After a few weeks, begin fertilizing the plants with tablets made specifically for water gardens. If the water becomes murky, be patient; an initial algae bloom may correct itself. If algae persists, use a natural product, such as Pond Saver, which is available where you buy plants. Never use soap to clean the glass; even a trace of detergent in the water makes it difficult for a plant to breathe underwater. As attractive as aquatics and semiaquatics are, keep in mind that a few of these vigorous plants can be invasive. Enjoy them at home, but never introduce them into a pond outside.