What is a Rain Garden?
A rain garden (or bioretention basin) is essentially an area situated in a low-lying bit land planted with native perennials and shrubs. This planted area has one job: to absorb and store stormwater runoff. Rain gardens are an elegant solution to excess runoff and are particularly useful in watersheds because of their ability to reduce pollution and improve water quality downstream. These projects prevent water fouled with automotive fluids, sediment, trash, and pet waste from reaching rivers, lakes, and – instead allowing pollutants to be absorbed by deep plant roots as stormwater infiltrates.
Rain gardens may sound like small-scale features good for helping homeowners deal with runoff, this storm water solution has utility far beyond the backyard. Rain gardens can be installed at larger scales, such as in suburban parks, apartment complexes, and in parking lots islands– but in these larger applications they are often called “bioretention basins”– which doesn’t have the quite same ring as “rain garden.” Nonetheless, the functions are the same, no matter what we call them.
Advantages of Rain Gardens
As green building standards become more mainstream and demand for sustainable design grows, rain gardens are likely to play an ever-greater role in stormwater management. Multifamily developments can earn LEED points for including rain gardens in their site design, which means that contractors with rain garden design and installation know-how will have a competitive edge in the bidding process.
In tests, large-scale rain gardens in public parks have consistently exceeded their rainwater containment capacity targets by 5 to 10 times for storm event volume. Factoring this into overall savings of as much as a 50% over conventional site drainage systems, the additional up-front cost of site work associated with large-scale rain garden installation seems more than worth it.
One final advantage over conventional site drainage is visual– well designed perennial plantings means that rain gardens perform double-duty: in addition to helping mitigate flooding and easing drainage issues, the project adds significant aesthetic value to a site. Perennial plantings offer low-maintenance, year-round visual interest with the added bonus of providing valuable habitat and food for birds, butterflies, pollinators and many other beneficial insects.
Planting for Rain Garden Success
Perennial plantings are the name of the game for successful rain gardens, and its easy to understand why: these plants are perfectly adapted the the region’s climate and can withstand dry periods without requiring irrigation. When the rain does come, these local natives are ready and willing to endure a little inundation while they soak up as much water as possible. G & S Nursery has you covered, and has some suggestions for which plants you will want to use in your rain garden project.
Perennial grass varieties create a dense ground cover that deters weeds and generate seasonal interest as they mature and go to seed each year. Clumping grasses are great for mid zones and edges of rain gardens. Hameln grass (Pennisetum alopercuroides) and Fakahatchee grass (Tripsacum dactyloides) form clumps that will grow a halo of pale seed heads each fall, and Muhly grass (Muhlenbergia capillaris) will add cotton-candy pink tufts of texture. Soft rush (Juncus effusus) is great for areas at the center of the garden that will experience the most moisture and take the longest to dry out.
Flowering plants will add interest and color throughout the year and will provide pollinators with food and habitat as well. All daylilies (Hemerocalis spp.) thrive in the lower, shadier sections of rain gardens, and crinum lilies like Crinum augustum ‘Queen Emma’ with their height and showy blossoms will steal the show when they are in bloom.
Hibiscus species also like to stay moist and will send up tall stalks with long-lasting floral displays from the midzones.
Bicolor iris (Dietes vegata ‘Bicolor’) with its grassy profile will bloom profusely through several seasons and does well along the drier edges of rain gardens. Rudbeckia Goldsturm offers brilliant yellow blossoms that make it a perfect flowering plant for the edges of the rain garden. Buddleia is hardy and blooms profusely summer to fall, making it an ideal candidate for areas of the rain garden that receive full sun. Hydrangeas, particularly Hydrangea quercifolia, can add density and texture to the deeper reaches of a rain garden, and give fantastic seasonal shows between blossoms and showy fall leaf colors.
For large-scale rain gardens, some anchor plants will offer color and texture even through the dead of winter. Evergreen shrubs are well-suited for this job, with Buxus spp giving reliable density and texture, Walter’s viburnum offering flowers from winter to spring, and Dahoon holly popping with bright red berries. Wax myrtle is also a winner and is more drought and damp tolerant than most. Papyrus and Saw palmetto plants are a different type of evergreen, lending excellent, tropical texture to the mid zones of a rain garden.
While most small-scale rain gardens need no such large features, a public-scale project will benefit from the addition of a selection of trees. For areas with serious rainfall, Bald cypress (Taxodium distichum) and River birch (Betula nigra) are ideal trees, both thriving in marshy, wet soil. Weeping willow (Salix babylonica) provides lovely texture and Red maple (Acer rubrum) or Sweetgum (Liquidambar styraciflua) lend a splash of color in autumn months.
Rain gardens are an innovative and sustainable solution to on-site stormwater management, and may add significantly more value than traditional systems. While the engineering is up to you G & S Nursery is happy to help you with the plant material you need to make your bioretention project a success.
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