Water lilies are beautiful plants, perfect for water ponds. They come in several varieties, with different colors of blooms ranging from pink to blue to white; and different sizes ranging from tiny to several feet across. But there are some disadvantages to raising water lilies. They will not suit every pond, which is why you must make sure they are right for you before purchasing them.
Water lilies grow rapidly and voraciously, just like many other aquatic plants. This occurs when there is an excess of nutrients in the pond water. With smaller ponds, water lilies can completely cover the surface in just a few short weeks. This is dangerous because it will reduce light penetration into the pond and kill fish and other plants. This problem will be even more evident with warm water temperatures during summer months, because it keeps oxygen-consuming animal respiration and decomposition rates high, reducing the oxygen in the water. Water lilies shouldn't be planted in very shallow or small ponds. Clear water in ponds also allows lilies to shoot their stems even more quickly then usual. Unless the water lilies are regularly maintained and pruned, they can be a disadvantage for a pond.
Regular maintenance is a must for water gardens that have water lilies. The plant must be cut, harvested, pruned and maintained with aquatic herbicides. In the growing season, water lily leaves should be pinched off every day. If water lilies are left to die and decompose, this creates mats on the water's surface that are unattractive and crowd out live plants. In the springtime, water lilies must be fertilized heavily--usually every two weeks--because they are voracious feeders. You will also need to change the water frequently in the pond so it does not get bogged down with the lily fibers. You can hire a professional to do this, but that can get expensive.
Water lilies have two major insect problems. Black aphids cause water lilies to have yellowing or browning leaves. You will see small black insects scattered on the leaves and pads. Aphids can come with new plants or just be attracted to water ponds. The bugs infest water lilies to suck the sap from the leaves. To get rid of aphids, hose them off into the water for the fish to eat, and remove the damaged leaves from the plant. Aquatic leaf beetles are another insect to watch for. These can be recognized by holes all over the water lily leaves that are chewed by the beetles, along with dark, speckled areas on the leaves. Keep the dead leaves or stems out of the pond. Check the underside of the leaves for eggs and remove the larvae. Apply insecticide to get rid of these during the growing season.