More than Just a Pretty Garden
After a wet spring when rain was abundant in Chesapeake Country, we are now in the midst of a heat wave with chance blasts of short-lived rainfall.
Most of the water that fell for 15 days straight from April 27 through May 11 washed unimpeded into our rivers, flooding streets and carrying whatever was in its path into the Bay. The luckiest raindrops were caught by thirsty native plants and flowers and held in a rain garden just long enough to send that water into the soil below, clean and filtered from pollutants.
Rain gardens are the darlings of stormwater retention systems. These shallow depressions are usually constructed near driveways, walkways and parking lots to catch the runoff from nearby impervious surfaces.
The gardens’ primary function is to improve water quality by allowing stormwater to soak into the ground — instead of flowing into storm drains or straight into rivers and the Bay, causing erosion, pollution and flooding. Beyond that function, though, they are delightful elements of our spring and summer landscapes, pretty in themselves and welcoming to all sorts of bird, butterfly and bee activity.
Hang around Chesapeake Country long enough and you can spot the rain gardens hiding among the parks and landscapes of familiar places.
The Secret Rain Garden
“Over the river and thru the woods, to Shady Side’s secret garden,” says MaryBeth Austin as she walks the mulch path lined by the happy faces of black-eyed Susans and purple coneflowers in the gardens at the Captain Avery Museum.
Austin, a graduate of the Master Watershed Steward Academy and museum volunteer, hopes that the secret gets out about the lush and thriving rain gardens and inspires visitors to create their own personal watering holes.
“This truly is something anyone can do at home,” adds Gerry Robertson, executive director of the museum. “The gardens add grace and peace to our grounds.”
But do they work? Do they do all that they promise? How do they function in both flood and drought?
Rain Gardens at Work
The Captain Avery rain garden was installed in 2012 to catch rainwater while being aesthetically appealing and functional. Austin helped create the garden as her capstone project for the watershed steward program.
“The gardens have proven themselves time and time again,” Austin says. “Heavy rains pour down, but within 45 minutes, the water has soaked through the ground — as it was designed to do.”
Two days later, the water has filtered off the surface and down into the soil, draining approximately five acres surrounding the museum property.
Watershed stewards are taught the “three S’s” of stormwater retention: Slow it down, spread it out and soak it up. Rain gardens accomplish all three, even when the rain is scarce. They help replenish the groundwater supply — important during times of drought.
“Rain gardens are built with deep layers of soil that allow not only great filtration but also generous root development in plants,” Austin explains. “Having those deep roots really helps in times of less moisture.”
Native plants that can handle moisture as well as periods of drought include black-eyed Susans, coneflower and native grasses such as Oehme palm sedge and hardy perennial hibiscus.
The garden structure consists of an absorbent soil bed, a layer of mulch and plantings that absorb pollutants such as excess nutrients. The shallow-ponding design helps slow down the water. Having a variety of plants of differing heights provides shade for the less drought-tolerant plants.
Rain Gardens around Town
Spa Creek Conservancy in Annapolis has installed about 100 rain gardens in the decade since its founding. In such a developed area, many are in businesses — as well as at most churches in the Spa Creek watershed. You can see this “rainscaping” at Annapolis Hyundai, Koons Toyota, Pinkeys Liquors, Blackwall Hitch, Amos Garrett Park, Monticello Avenue, Cheston Avenue and W&P Nautical. Bay Weekly’s own rain garden, a Spa Creek Conservancy project, is in full bloom with cattails, flowers and grasses — an oasis for birds, bees and butterflies.
Spa Creek Conservancy’s Mel Wilkins says the only way a properly designed and installed rain garden will fail is if it isn’t maintained.
“The best way to know if a rain garden is doing its job is to see how the plants are doing. If they are still growing and thriving, that means they are taking up nutrients from the soil, nitrogen and phosphorus that we don’t want in the Bay. If water is still in the garden after 48 hours, something isn’t functioning correctly.”
Rain gardens are not maintenance-free, Austin agrees.
“They need to be cleaned out at the end of each season. We spend from February through spring cleaning out dead plants and decaying matter,” she says.
Spa Creek Conservancy recommends cleaning up trash and debris after storms, replacing dead plants and weeding annually.
“Add a little layer of mulch — two inches — every year, and clean up the silt deposits every two to three years,” Wilkins advises.
Considering that 75 to 80 percent of pollutants are picked up in the first inch of storm runoff, rain gardens are a beautifully effective line of defense.
Create your own: http://bit.ly/BayWeeklyRainGardens.