A rain garden is a shallow, planted basin that catches water from a roof, driveway or slope and lets it soak in over a day or two. It isn’t a pond and it shouldn’t hold water long enough for mosquitoes. Done well, it just looks like a lush bed that happens to be a few inches lower than the lawn.
Where it goes
At least ten feet from the house foundation, away from septic fields, and not directly over utility lines. Do a simple test: dig a hole a foot deep, fill it with water and time it. If it drains within a day, you’re in business. Heavy Piedmont clay often needs the basin amended with compost and coarse sand.
What to plant
Natives that tolerate both wet feet and dry spells: swamp milkweed, blue flag iris, joe-pye weed, cardinal flower and switchgrass in the wettest centre; black-eyed Susan, coneflower and little bluestem on the drier rim. Plant in drifts of three to five so it reads as a planting, not a collection.
Mulch with shredded hardwood, which stays put when water flows through better than pine bark nuggets do.
Size and upkeep
A rough rule is a basin about a fifth of the hard surface that drains into it. After the first year, upkeep is a spring cutback and pulling the odd weed. No watering, no fertilizer.