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The Rural Voice, 1998-08, Page 48Gardening The pond - a sensitive mini -ecological system By Rhea Hamilton -Seeger In learning about water plants I have gained some sympathy for my friends who are taking up gardening for the first time. It is a whole new area for me and full of exciting new ideas and challenges. Just like any other garden you have to establish what conditions your plants will be growing in. Light and water depth are the most obvious. The size of your pond will determine if your plants can overwinter or have to be brought in and if you have fish, please be warned that they like to graze and you will therefore need to consider extra plants for them. If you are planning on growing water lilies, you should know they need a minimum of six hours of sunlight. A pond is a sensitive mini - ecological system. If working well, it will have clear water, healthy, lush plants, a variety of toads and frogs and hopefully a few dragonflies. But if the balance is disturbed, then the water will cloud, plants or fish could die and the worst case would be a disturbing odour. So you want to research and build carefully. There are three types of aquatic plants: submerged, floating, and marginal. You need a number of each to maintain a balance in oxygen levels and nutrients in the water. Submerged plants like Elodea Canadensis or Canadian pond weed are invaluable to oxygenating the water and competing with algae for nutrients. Calculate about five bunches per square metre of pond surface. If your pond is deep enough native plants will winter over. Excess plants can be composted. Hornwort (ceratophyllum) is another submerged plant that offers spawning areas for fish eggs. They are especially easy to plant by adjusting fishing weights to the bottom of the bundles and easing them into the water. Floating plants include water hyacinth and water lettuce. Both have long trailing roots that absorb 44 THE RURAL VOICE nutrients from the water and provide shade. But since both are tropical they will not winter over. Smaller plants like duckweed and fairy moss multiply quite quickly and all of these can be controlled by merely scooping out excesses with a net. These are native, not as showy as the hyacinth and water lettuce, but will winter over. In our pond there are 14 rather large goldfish and we have had to resort to raising duckweed in a submerged tub and then feeding the fish twice a week with it. We just can't get enough floating plants in the pond to help the water quality without the fish consuming it all. Even the water hyacinth and water lettuce get chased around and their trailing roots are nibbled down to stubs. The alternative is to offer lettuce to the fish but they prefer the floating plants. Water lilies, water hawthorne and floating heart are grown in soil but their leaves grow to float on the surface. These are considered deep water aquatics and while they don't take as many nutrients from the water they do offer shade which helps reduce algae. Since most submerged aquatics require sunlight and there should be some pond surface open for oxygen, you should limit your floating plants to 60 per cent of the pond's surface. Hardy water lilies send up fresh growth each spring and moving them to shallower water helps warm the plants and get them off to an early start. They can then be moved to the deeper section as the pond warms up. We don't like the extra work and leave the lilies where they are. It just makes for a slower start for the lilies. Your water lilies should be planted in mesh or chicken wire baskets lined with untreated natural hessian to keep the soil from leaching out. If you are going to leave the lilies for more than one season you should use a double layer of burlap. This allows the roots to seek nutrients unobstructed. If you use a smaller pot or a three to four - gallon nursery pot to make it easier to handle, you will have to repot these each spring. Don't forget the pea gravel on top to keep the soil from leaching out. Avoid decorative gravel as it may affect the water. Marginal plants add shape and structure to your water garden. They can be set in pots and placed in the water to a depth of three to six inches or grown around the edge of the pond. Marginal plants include such favourites as cattails, marsh marigolds, arrow arum, arrowhead and blue flag and pickerel weed. We created an island in the pond by turning a large pot upside down and placing a large flagstone on top. This acts like a table below the water and then we set out pots of cattails (Typha angustifolia), blue flag iris (Iris versicolor) and pickerel weed (Pontederia cordata) here. The cattails offer height while the iris and pickerel weed offer interesting foliage and blue blossoms from spring to mid summer. Most marginal plants can be potted in standard garden loam, with a good layer of pea gravel or sand on top to prevent the soil from muddying the pond. The pea gravel also keeps the fish from routing out your plants. This column barely scrapes the surface of pond gardens but it does get you off to a good, running start. Remember it is easier to plan first and avoid problems later. Check out your local garden centres for information as well as your library. Take a look at the.local creeks and ponds to see what looks good and what survives your winter. And don't be shy about asking your neighbour with the pond for advice. Sometimes the best information comes from those who have suffered through a problem and come up with a solution.0 Rhea Ilamilton-Seeger and her husband raise two children at their home near Auburn. She is a skilled cook and gardener.