If you are primarily interested in aquatic plants you will derive a great deal of enjoyment from a marsh garden. Many plants thrive in places where the ground stays wet all year, and they come in the loveliest shapes and colors. Anyone building a pool should at the same time set up a marsh bed or garden near it because a marshy area not only supports beautiful plants but also offers an environment that is attractive to many animals.
What You Should Know: Since a separate marsh garden receives no water from a pool you have to check frequently to make sure the water level or soil moisture is still adequate.
– The size of the marsh garden depends entirely on your available space. The only thing that matters is that the entire excavated area be about 10 inches (25 cm) deep. Otherwise the marsh will dry out too quickly on hot days.
– Fill the marsh area either with earth from the bottom of the pool (the disadvantage of this method is that it is hard to check the moisture level of the soil) or simply put the plants, set in containers, in the marsh garden.
Location: A marsh garden can get full sun because most wetland plants do well in the sun; partial shade is fine too.
Materials to Seal the Bottom: Any somewhat large, shallow basin that holds water will do¡ªa play pool that is no longer being used, a retired children’s plastic splash basin, or a fiberglass shell. Flexible liner is inexpensive and very practical, but it has to be at least 40 mils (1 mm) thick because some aquatic plants (reeds) have roots strong enough to push through thinner liners. Pull the liner over rocks or square beams around the marsh bed’s edges, making sure that the ends stick up. The ends of the liner have to stick up beyond the planned water level (or the surface of the marsh soil) or else the surrounding, drier earth will draw moisture out of the marsh garden.
Plants: The smaller a marsh bed is, the more you should avoid plants with a tendency to spread. Some plants that are well suited to a small area¡ªless than 20 square feet are marsh marigold (Caltha palustris), water forget-me-not (Myosotis palustris), Siberian iris (Iris sibirica), bog arum (Calla palustris), cotton grass (Eriophorum angustifolium), golden club (Orontium aquaticum), and, of course, dwarf cattails (Typha minima), bur reed (Spargan-ium erectum), and purple loosestrife (Lythrum salicaria).
Different wetland plants require different kinds of soil. Some like soil that is alkaline while others prefer acid soil (containing peat). You can solve this problem by setting the plants into individual containers, each with the right kind of soil for the plants in it.
Animals: A marsh garden attracts many creatures. Just which insects, amphibians, and other animals will be drawn to your marsh depends on the rest of the garden and on the surrounding area.
The Margin: Natural, untreated wood, roots, and fieldstone always look nice in combination with plants.
Upkeep: Check the moisture level frequently and, if necessary, water with a garden hose. A marsh garden should never dry out completely. Plants that spread too vigorously have to be thinned now and then. In October, tall marsh plants should be cut back by nine-tenths. Spread the stems and leaves you have cut on the plants as insulation against freezing and wait until March before you throw them on the compost.