Building A Rain Garden
By Kathleen Harvey, AAP Columnist
There is an old saying: “April showers bring May flowers.” We’ve had a wet spring, which has brought a bounty of beautiful, fragrant flowers in many colors, sizes, and shapes. But what if there is a low spot on your property, one that turns into a large puddle every time it rains? It won’t take much for that space to become a breeding ground for mosquitoes, or a mud puddle for pets and children. One way to solve the problem is by building a rain garden, a space filled with flowers and shrubs that benefit from periodic flooding.
A rain garden receives water from impervious surfaces such as rooftops, downspouts, sidewalks, driveways, and patios. Water is absorbed into the soil through the network of deep plant roots. The shallow depression of the rain garden holds water so it can slowly infiltrate back into the soil as the plants naturally remove pollutants from the runoff. A rain garden should be designed so that water drains the space within 24 hours.
The first step in designing a rain garden is to define a low spot in the yard. Position your rain garden at least 10 feet from your home. If your rain garden is too close to the house, it may erode the home’s foundation or seep water into the basement over time. Plot your garden’s size using stakes and string. Next, construct paths to channel runoff from the gutters and higher parts of the yard to the rain garden.
Use a mix of plants adapted to different water depths, along with desired design features. When deciding which plants should be placed where, think of it as a large container garden, with thrillers, fillers, and spillers. Thrillers are a tree or large shrub that creates the focal point of the space. Fillers are shorter, clumping perennials that surround the focal planting. Spillers are plants that line the outer rim and won’t be badly damaged by sloppy lawn mowing or weed whackers.
Plants for each rain garden will vary depending on how much water the garden will hold, the amount of sun exposure in each day, and the soil conditions. Start planting in the deepest part of the rain garden, whether it’s in the middle, or on a property line where your neighbor’s soil level is higher than yours. This area will hold the most water for the most amount of time. Examples of plants that are tolerant of inundated, (i.e. flooded) conditions that can tolerate standing water for a period of time, and are good for the tall focal point include: elderberry (Sambucus canadensis), which is great for jams, jellies, and wine; ninebark (Physocarpus opulifolius); viburnum; silky dogwood (Cornus amomum), whose stems turn brilliant red in the winter for winter interest; spicebush (Lindera benzoin); swamp azalea (Rhododendron viscosum); and winterberry (Ilex verticillata).
Perennials for filler spots include blue flag iris (Iris versicolor); blue vervain (Verbena hastata); cardinal flower (Lobelia cardinalis); ferns; asters; swamp rose mallow (Hibiscus moscheutos); and swamp milkweed (Asclepias incarnata), which is monarch butterfly food.
For areas that are less swampy, but get inundated during summer downpours, several shrubs are a great addition. American beautyberry (Calicarpa americana) gets pretty purple berries in fall. Red-osier dogwood (Cornus sericea) and sweet pepperbush (Clethra alnifolia) feed bees and other pollinators. Perennials that like wet feet include blue false indigo (Baptisia australis), blue star (Amsonia tabernaemontana) and mistflower (Eupatorium colestinum).
A few trees that will grow in our area and thrive on periodic flooding include the fringetree (Chionanthus virginicus), ninebark (Physocarpus opulifolius), red maple (Acer rubrum), serviceberry, and my personal favorite, paw paw (Asmina triloba) which produce wonderful edible fruits with a custard like flesh.
So if your property is less than completely flat with a low spot that just doesn’t drain well after a thunderstorm, think about building a rain garden! If your wife, mother, or grandmother is a gardener, help her design and build a rain garden for Mother’s Day. Everyone can participate and enjoy it.
Happy Mother’s Day!
