Wetlands provide the ideal environment for moisture-loving plants. From grasses and ferns, to flowering perennials, shrubs, and trees, wetlands also serve as a valuable source of food, shelter, and nesting sites for winged wildlife like butterflies and hummingbirds, and especially dragonflies and damselflies.
While few backyards have the space for the types of large wetlands found in nature, you may already have a prime location for setting up a smaller wetland garden. Potential prime areas include a soggy spot that drains poorly, a depression in the landscape that holds water, or any naturally occurring damp area in your yard. The site may have standing water year-round, or only during the rainy season.
Even if your yard lacks a low lying area or wet spot, you can still enjoy the benefits of a wetland garden on a more minute scale. Design options in this case include a border or island in a freestanding oasis, or a dry land transition neighboring a backyard pond.
Whichever option you choose, the goal is to create an area that retains moisture without being completely watertight. Here's the skinny on making your own miniature backyard wetland.
Gather your materials and tools
Before you start digging, gather your tools and calculate the size of your wetland and materials needed. As for tools, you will need a garden hose, heavy rope, or powdered limestone for marking the site; a shovel and pick for digging; and a measuring tape, rake and sharp scissors, or utility knife for cutting the liner.
Essential materials needed include coarse sand or gravel, a flexible pond liner, and edging materials such as stone or brick. The amount of sand or gravel required will depend on the size of your wetland. You will also need loamy garden soil, which many of us gardeners lack. However, you can easily make your own by mixing two parts garden soil with two parts compost, two parts peat moss, and one part sand or vermiculite.
To determine how much coarse sand or gravel you will need, start by calculating the number of cubic feet needed. Simply convert the wetland's dimensions to inches, then multiply the width times the length times the desired depth of sand or gravel (usually 1 or 2 inches) and then divide by 1,728 (the number of cubic inches in a cubic foot). For example, to fill a 4-foot by 3-foot wetland with 2 inches of sand or gravel, you will need 2 cubic feet of sand or gravel (48 times 36 times 2 divided by 1,728).
To calculate the size of the liner, measure the wetland's maximum width and length, then add to each dimension two times the maximum depth plus 2 feet. For example, measuring in feet, a 4-by-3-by-2 wetland will require a 10-by-9 liner (4+4+2=10 feet; 3+4+2=9 feet).
1. Choose an open and level site that receives at least five hours of sun a day. You can then use the garden hose, rope or powdered limestone to mark the wetland's outline on the ground. Then dig a hole with gradually sloping sides to a maximum depth ranging from 1.5 to 3 feet.
2. Remove any protruding roots or rocks from the site. Cover the bottom of the excavated area with a 2-inch layer of damp sand to protect the liner from potential punctures.
3. Line the hole with heavy plastic or a flexible, heavy-duty polyethylene pond liner by unfolding the liner loosely over the hole, leaving an even overlap on all sides. (The liner is easier to work with if you install it on a warm, sunny day.) Smooth the liner into position.
4. Since the area needs to be water-retentive, not watertight, use sharp scissors or a utility knife to puncture the liner around the sides about halfway up from the bottom, placing punctures about 12 inches apart for a smaller wetland, or up to 3 feet apart for a larger wetland. Leave a 6- to 12-inch overlap and then trim off the excess.
5. Once the liner is in place, cover the bottom with a 1- to 2-inch layer of coarse sand or gravel. Next, fill the area with a nice loamy soil that retains moisture, then place rocks or stones around the wetland's edge to cover the overlap and secure the liner in place.
Maintaining your wetland
If you want your wetland plants to flourish and attract winged wildlife, keep the soil moist to slightly moist at all times. A densely planted wetland works best since it allows less evaporation than one with areas of exposed soil surface. A mulch of compost or leaves will help retain moisture and shade the surface until the plants fill in.
When moisture does evaporate, you may need to water your wetland garden. Be especially vigilant during periods of hot, dry weather. Before too long your miniature wetland will become a welcome source of food, shelter and nesting sites for a variety of winged wildlife and a pleasing place to relax and enjoy the sights.
--Kris WetherbeeRick Wetherbee
Start with this list of wetland recommendations and then check with your local nursery or garden center to find out which might work best for your situation. Keep in mind that a select few may show mildly invasive tendencies depending on the location. If this is the case, simply grow them in containers sunk into the wet soil to maintain control.
Plants for shady moist or wet soil
Golden sedge (Carex elata 'Aurea'); Gunnera manicata or G. tinctoria; Jack-in-the-pulpit (Arisaema triphyllum); marsh betony (Stachys palustris); marsh marigold (Caltha palustris); meadowsweet (Filipendula spp.);
monkey flower (Mimulus guttatus) and scarlet monkey flower (M. cardinalis); moor grass (Molinia spp.); plantain lily (Hosta spp.); tufted hairgrass (Deschampsia cespitosa); turtlehead (Chelone lyonii)
Plants for sunny moist or wet soil
Astilbe (Astilbe arendsii); bog arum (Calla palustris); bog rosemary (Andromeda polifolia); cardinal flower (Lobelia cardinalis); cattail (Typha spp.); camas (Camassia spp.); common calla (Zantedeschia aethiopica); iris-blue flag (Iris versicolor) and Japanese water iris (I. ensata); New England aster (Aster novae-angliae); rush (Juncus spp.); swamp milkweed (Asclepias incarnata); sweet flag (Acorus spp.); switch grass (Panicum virgatum); water hibiscus (Hibiscus moscheutos palustris); water plantain (Alisma plantago-aquatica)
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