What is a rain garden? How is it different than a pond? Who should plant one?
Sally Boswell, education and outreach coordinator for the Center for Inland Bays, answered all these questions and more for the Fenwick Island Environmental Committee on Wednesday, Oct. 8, at town hall.
According to Boswell, a rain garden is a depressed bed of soil dug about 2 feet down and enriched with organic matter and then filled with plants native to the area. The native plants allow the soil to absorb rainwater more effectively than other non-native plantings and other landscaping techniques.
That’s important, as rain gardens are designed to promote pooling of water that comes from downspouts and paved surfaces – they are not ponds. Gardeners are encouraged to locate a rain garden where rainwater tends to collect in their yard.
Boswell added that the difference between a rain garden and a regular garden is that rain gardens are designed to handle more water and need no fertilizer. When just starting out, though, they will need to be watered until the plants are established. After that, rain gardens are very low maintenance.
Boswell explained that the coastal area, with its salty soil, is perfect for rain gardens.
Rain gardens themselves are a bonus for the environment. Boswell explained that impervious surfaces, such as roads, driveways, and pavements, don’t allow for adequate drainage of rainwater. The water simply rolls faster into rivers, streams and canals and, eventually, into the ocean. When surfaces are more permeable – such as grass or gardens – the rain water is allowed to slowly trickle into the earth and along the way sheds much of the excess nutrients it carries that can be harmful to the water supply in the aquifers below.
“Stormwater is one of the biggest threats to our waterways,” said Boswell. “We protect our waterways when we reduce runoff.”
“As areas have become more urbanized, rain has to find a new path to our wetlands, and along the way it collects pollutants, such as grease, oil, copper and mercury – all of which eventually end up in the inland bays. Rain gardens are a sustainable and economical way to deal with the water,” explained Boswell.
She also noted that a 1,000-square-foot roof yields 600 gallons of water from a 1-inch rainfall. “And rain gardens absorb 30 percent more water than the same size lawn,” she added.
Boswell said that, by replenishing the aquifers through recharging the water that gets into the ground, rather than sending it down a storm drain, rain gardens allow people to capture the fresh water instead. “And it doesn’t allow the water to go out into the ocean, where it is lost.”
“You want the gardens to be 10 feet or so away from foundations, underground utilities and septic drian fields,” said Boswell. “They should drain in about 12 to 15 hours. You’ll want to prepare your soil with two parts sand, one part topsoil and one part compost, and loosen to a depth of 2 feet – and if you plant them, they will come,” she added, referring to the native birds and pollinators such as butterflies, dragonflies and honeybees.
Boswell noted that the town of Millville has a demonstration garden at its town hall, and she is looking to emulate a program – with a goal of creating 10,000 rain gardens – that is currently running in Kansas City, Mo. She said she would like to have something similar in the inland bays watershed area, with 1,000 rain gardens, starting with the towns and town halls themselves.
“The big objective is slowing water down, so it has time to sink in,” she said. “And in working with areas that towns have control over, towns have a great opportunity for little decisions to turn into big results.”
For more information on native plants suitable for the area, visit www.delawarewildflowers.org online. Some native plants for Delaware include lady fern, pink turtlehead, great blue lobelia, Culver’s root, siky dogwood (shrub), inkberry holly and winterberry holly (both shrubs). For more suggestions or information rain gardens and native plants, visit http://ag.udel.edu/extension/horticulture/raingarden/index.htm.