We GriffinTeckers love the big old building we work in. We love its location, close to the heart of Nashville. We even love the parking lot (the running joke in Nashville being that the music industry is the second-biggest business in Music City, right behind Parking). The thing that makes our parking lot easy to love is a spot of life and color squarely in the center of it. It’s a thing called a rain garden.
What’s a rain garden, and what’s special about it? I posed these and other questions to Tom Boyd, landscape architect with EDGE, the urban design firm responsible for the creation of Griffin’s rain garden.
A rain garden is basically a planted depression in the ground designed to accept the water we accumulate on our roofs and pavements and allow it to do what it wants to do in the first place: soak into the ground. Tom’s worked on a wide range of projects around the country, and he says that Griffin’s Sawtooth Building site offered some unique challenges. “The rain garden at Griffin was an evolving design that started out with only low growing perennials, but transformed into a more layered concept with various flowering perennials, shrubs, and small trees. All of the plant materials used are native or naturalized species that tolerate the weather in Middle Tennessee, and will thrive without using fertilizers, and little or no additional watering. The perennials used include purple coneflower, butterfly weed, and blackeyed susans. The shrubs include Virginia sweetspire and swamp mallow, while the small trees are sweetbay magnolias.”
Most of the rain gardens that EDGE designs are commercially scaled facilities known as bioretention areas. They’re typically utilitarian designs used on large sites with lots of roofs and pavement. Aside from filtering rainwater through the soil, one of the most important functions of a rain garden is to slow the destructive rate of runoff produced by urban sites. Without such natural areas, rainwater gathered by roofs and parking lots causes erosion, washing away soil, muddying creeks and streams, and causing pollution in rivers. Including a rain garden in the design of an urban landscape goes a long way toward mitigating the negative environmental impact of pavements and buildings.
But, though they are an effective, and a cost-effective, solution to what would otherwise be a huge problem, rain gardens are far more than merely functional. They affect the lives of the people who live near them in many subtle and positive ways. Tom says, “One of the more intricate designs we have completed was for a new multi-family building in east Nashville on Dickerson Road, called Uptown Flats. The construction was just completed this past spring, and everything is really starting to grow well. But I would have to say that the Griffin rain garden is the one I am proudest of, as it has a much more intimate scale, and relates well to the building entrance and surrounding landscaping.”
Rain gardens are not exclusively the province of landscape architects and urban planners, either. Tom says, “If you have enough space, a rain garden is a great addition that is both attractive and serves a crucial environmental function. Residential rain gardens are becoming very popular, especially as many homes are being designed and built to minimize their impact on the environment. The three primary characteristics for a successful rain garden are: soil that drains sufficiently, a downspout or other source of concentrated rainwater, and as much sunlight as possible. But if your yard is lacking one of these characteristics, don’t fret; you can work around it.”
Tom’s firm is not directly involved in the ongoing maintenance of the rain garden at Griffin. He gives major credit to the individuals who take care of it. “They do a fantastic job, and are equally responsible for its outstanding appearance.” I spoke with Rick Herod, who does weekly maintenance on the site. At first he seemed surprised at my interest. Then he warmed to the subject, explaining about the plantings and how they work together. Rick works from a map that identifies the plants, but he was able to tell me off the top of his head their names and preferences, from the exotic-sounding Virginia Sweetspire, to the exotic-looking Swamp Mallow, with its huge funnel-shaped flowers that seem to glow off the end of the spectrum into the ultraviolet.
A surprise inclusion is Butterfly Weed. Anybody growing up in rural Middle Tennessee is familiar with this lanky milkweed and its bright orange-red flower heads that bloom all summer. Some know it as Pleurisy Root, a nod to its use by Native Americans for lung ailments. Its other common name acknowledges it as a favorite food plant of Queen and Monarch butterflies. It’s hardy and common, but unlike many plants that grow in waste places, it somehow avoids becoming an invasive pest. Here in Griffin’s rain garden, it assumes its rightful place as a tall, brightly-colored native wildflower.
Not all occupants of the rain garden are as well-behaved. Rick fights an ongoing holding action against invading Johnson grass and sedges, species that will take over and crowd out the diversity of plants desirable in any garden. Weekly maintenance is necessary; as Tom Boyd observes, “When it comes to landscapes, good design will take you only so far.” But as far as maintenance goes, a well-designed rain garden is largely self-sustaining through periods of downpour and drought, alike.
During one of the recent Nashville downpours, I slapped on a wide-brimmed hat and wrapped my Marmot around me, and ventured out to observe our rain garden in action. Griffin’s parking lot slopes down steeply from the street, and during any substantial rainfall, water streams down the pavement from the entrance. Standing in it, my shoes push up a bow wave of rapidly flowing water. Up on Lindell Avenue, I walk along the curb, following the flow of the runoff along the gutter. As the water disappears down a storm drain, the turbulence and energy of the flow is clearly visible.
Then I walk down the drive toward the middle of Griffin’s parking lot. I watch as sheets of water flow down the wide pavement, toward the easements in the curb surrounding the rain garden. Passing through the curb, water first encounters an area of rounded river rocks. The shapes of the rocks break up the larger movements of the water, like pushing it through a shower head. The water, its movement thus softened, is introduced into a thick layer of mulch that further diffuses it into the soil among the roots of the plants. By the time the water reaches the bottom of the shallow funnel that is the rain garden, there is no runoff. There is only water doing what water does naturally, soaking the soil and eventually filtering down to the embedded drains. Shorn of its kinetic energy along the way, the water carries almost nothing of the clay and silt that would otherwise muddy the Cumberland River downstream. The energy of that water, instead, finds its way up into the stems of black-eyed susan and coneflower and magnolia, and bursts forth against the background of the Nashville skyline as pink and purple and gold blossoms, heavily visited by bees and butterflies. Instead of just a way to deal with a rainwater “problem,” we have an oasis that we visit every time we walk to or from our cars.
Interested in a rain garden of your own? Tom Boyd suggests you check out Low Impact Development, The Rain Garden Network, and Rain Gardens For Nashville. There’s info here about working rain gardens in the Nashville area, but equally applicable wherever it rains, describing exactly how to create a rain garden. Rain Gardens for Nashville in particular has a lot of info on their website, and does a good job of promoting the use of rain gardens, and assisting with installations at schools and parks in Nashville.
We at Griffin would like to thank Rick Herod for taking such good care of our rain garden; Tom Boyd and the people at EDGE for bringing it into existence; and, as always, Allen Arender, Joan Celli, and Susan Hartman of Holladay Properties, who take such pride and personal interest in making our Sawtooth Building a delightful place to work.
^michael, 2013 07 12