Water gardens can provide a unique adventure for the gardening hobbyist. Not only do they nurture more exotic plants than what we’d find in a typical flowerbed, but they can also be stocked with dazzling fish and even entice other creatures like frogs to come and live. Because water plants are not native to our backyards, however, they are dependent upon the structures that we build to support them.
These kinds of gardens present a variety of potential problems, including concerns about water quality and the stability of the pond liner, which can be avoided if we anticipate them in advance and plan accordingly. Before excavating a site, we should consider available sunlight, proximity of trees and shrubs, possible runoff contamination, and groundwater levels.
Water plants don’t need to be situated in full sun. Though water lilies prefer at least a few hours of sunlight a day, many kinds of aquatic plants will tolerate or even thrive in shade. Fallen leaves, however, not only mar the beauty and clarity of a pond but also threaten the life within it. Over just a few days, oak and maple leaves and pine needles will produce tannic acid, which can stress fish and even kill them. Trees also pose the threat of root intrusion, which can damage a pond’s liner. If it’s not possible to situate a pond away from trees and shrubs, consider building an aboveground structure and placing a screen over it during the leaf-falling season.
Ground surface runoff can dump a variety of contaminants into a water garden, including insecticides, herbicides and lawn fertilizers. If a pond is not elevated higher than the rest of the yard (about 4 inches in a heavy-rainfall area, 2 inches in dryer climate) it should be raised with soil from its excavation. Mulch and stone, or anything else that comprises a pond’s edging, can be tapered gradually back to the surrounding yard and provide it with a line of defense against runoff.
Groundwater pressure can crack molded or concrete ponds and cause a pond liner to bubble up. We can determine the water table in our yards by digging a test hole – deeper than the planned pond – and observing the water that it collects during the rainiest season. If the water table is higher than the depth of the pond, we may need to dig a drainage trench to redirect ground water away from it.
Planning around potential disturbances ahead of time can save us considerable time and money on tiresome repairs on our water ponds down the road. Then, instead of laboring, we can sit back and enjoy the natural wonders that we’ve managed to replicate in our own backyards.