Creating a Rain Garden

Creating a Rain Garden

By

Frank W. Porter

Porterbrook Native Plants

In recent years, the amount of damage to private and public property because of flooding has totaled billions of dollars. As mountains are reduced to negligible semblances of their former stature; as more highways are built and paved; as more and more new homes are constructed; and as more parking lots cover once productive meadows, the ability of the soil to absorb rainfall is limited. These impervious surfaces are areas that quickly shed rainwater into already overtaxed storm drains and nearby streams and rivers. The increased storm water runoff adversely affects every fiber of our natural environment and economy. Because this runoff is untreated, the amount of pollution from our own yards and gardens—which includes fertilizers, pesticides, herbicides, pet wastes, grass clippings and yards debris—is increased exponentially.

One way to help prevent these pollutants from pouring into our precious waterways and contaminating underground water supplies is to create a rain garden. A rain garden, quite simply, is an attractive and landscaped area which has been planted with native wildflowers, grasses and sedges that grow naturally in wetlands. These beautiful gardens are built in depressions which have been designed to capture and filter storm water runoff from rooftops and driveways around the home. Rain gardens offer countless benefits to the homeowner and the environment. A rain garden filters storm water runoff before it reaches local waterways. By slowing this runoff, it helps to alleviate flooding. Because it is actually a garden, it also enhances the landscape of individual yards. These native plants create a habitat and food source for wildlife, especially birds, butterflies, and bees. And the rain garden can safely recharge the ground water supply.

Constructing a rain garden does not have to be an expensive or complicated endeavor. A number of factors—the size of your yard, the amount of money you wish to invest, and the type of garden you wish to create—will determine the design of your rain garden. Whether your rain garden is large or small, it will help to solve water quality and flooding in your area. AND it will be a welcome and satisfying addition to your landscape.

Where should you build your rain garden and how large should it be? Your first task is to determine the drainage pattern of your property. Where does runoff flow? Are there areas where rainwater collects? Rooftops, paved surfaces, slopes and compacted soils usually are the largest sources of runoff. Once you have determined this information, you can find the proper location for your rain garden. A rain garden should be a minimum of ten feet from your house and your neighbor’s home to prevent any damage from water seepage. Never place a rain garden over or close to the drain field of a septic system. Do not place your rain garden in the area where water does collect. Instead, it should be placed up the slope from them in order to reduce the amount of water flowing into these wet areas. Rain gardens do best in a sunny or at least partly sunny location. Integrate your rain garden into your landscape with either a formal or informal design. Never place a rain garden beneath a large tree, because it might damage the root system of the tree. Be aware of underground utilities!

Once you have decided where to build the rain garden and the size it will be, you can begin to excavate and level the site. If the area has an existing lawn, you will have to remove the turf. Although herbicides can be used, this would be contrary to our purpose of eliminating pollutants. I recommend either placing black plastic over the turf to block sunlight or scalping the grass with a mattock (You can also rent a sod cutter for larger areas). Determine the perimeter of the rain garden. You can use a garden hose, rope, or stakes to define the area to be excavated. If your lawn is flat dig to a uniform depth, about four inches, throughout the garden. If the lawn has a slope, you will have to dig out the high end of the garden. The depth of a rain garden on a slope should not exceed twelve inches. The excavated soil can be used to raise the low area. Use the excavated soil to create a berm on the downhill side of the garden. The berm is a low earthen mound which surrounds three sides of the rain garden and will help to hold water during a storm.

You are now ready to plant your rain garden. This is an opportunity to enhance the beauty of your landscape. Choose native plants that are tolerant of both dry and wet conditions. By selecting a diversity of species you will not only create a stunning visual effect but also have healthier plants. Another factor to consider is the height, the bloom time, and the color of each plant. By using plants with different blooming times, you will extend the flowering season of the rain garden. Using different heights and shapes will provide depth and texture. And by randomly planting individual species in groups of at least three and repeating this throughout the garden will make a bold statement of color. Finally, incorporate not only wildflowers but grasses, sedges, and rushes to create a thick underground root system that will absorb the water.

Using native plants is the key to success with your rain garden. Native species are adapted to your local area. They do not require fertilizers. They do not need pesticides to thrive. And they survive downpours and droughts. The list of native plants to use in a rain garden is vast. Here are a few suggestions. Chelone glabra (White Turtlehead) offers spikes of elegant turtlehead white flowers, while Chelone lyonii (Pink Turtlehead) produces brilliant rose pink turtlehead flowers. The Baltimore Checkerspot butterfly will find your rain garden a favorite breeding site. Filependula rubra (Queen of the Prairie), with its showy pink flowers, will sway to and fro in the breeze. Liatris spicata (Dense Blazing Star) sends up dense spikes of purple flowers. Lobelia siphilitica (Great Blue Lobelia) and Lobelia cardinalis (Cardinal Flower) will brighten the edges of your rain garden with deep blue and red flowers. Physostegia virginiana (Obedient Plant), with its purple to pink flowers, should be planted along the inside edge of the berm. Its upright stems and dense roots will stabilize the soil of the berm. Eupatoriadelphus dubius (Coastal Plain Joe Pye Weed) has rounded pink flower heads and will provide stature without overpowering the rest of the garden. Iris versicolor (Harlequin Blue Flag), Iris virginica var. shrevei (Shreve’s Iris), and Iris fulva (Copper Iris) lend the appearance of cattails while offering colorful blooms. Symphyotricum novae-angliae (New England Aster), with purple to pink flowers, and Eurybia radula (Low Rough Aster), with lavender flowers, brighten the garden in late summer and early fall. Asclepias incarnata (Swamp Milkweed) will attract countless butterflies with its pink blossoms.

And do not forget the grasses and grass-like plants. Andropogon gerardii (Big Bluestem) and Spartina pectinata (Prairie Cordgrass) will tower above the wildflowers and produce interesting inflorescences. Elymus virginicus (Virginia Wild Rye) can be planted along the garden’s edge. Glyceria striata (Fowl Mannagrass) has unusual flower heads. Juncus torreyi (Torrey’s Rush) has round, orange seed heads. And Carex grayii (Gray’s Sedge) has seed heads that resemble a medieval mace.

Many other native species will grow successfully in your rain garden. The selection is limited only by your imagination. The reward will be a garden of native plants that becomes a home to countless beneficial insects and other wildlife and helps to protect our precious waterways.


Reprinted with permission of the Marietta Register