Improve Water Quality with Plants


Gardeners can use wetland plants to create a landscape that will capture, filter, store and slowly release storm water. These moist landscapes, known as rain gardens, trap and use nutrients that otherwise would run off and pollute nearby streams. A rain garden is a shallow depression that temporarily holds water. It may be an existing low area or it may be dug and shaped to hold water. The goal is to intercept water runoff and retain it long enough for it to percolate into the soil. In addition to filtering stormwater, rain gardens bring beauty and wildlife to the landscape.

Follow these steps to create your rain garden

  1. Estimate your roof ’s square footage. The rain garden should be about one third the size of the area. For instance, if the roof area is 200 square feet, the rain garden should be about 70 square feet.
  2. Choose a spot at least 10 feet from your house and downslope from the downspout.
  3. Before you dig, be sure you won’t encounter any utility lines. Call (800) DIG-RITE so utility lines can be marked.
  4. For a 200-square-foot roof, dig a shallow depression 6-to-8-inches deep and 10-feet long by 7-feet wide (adjust dimensions if roof is larger or smaller). Slope sides toward center.
  5. Test the overflow pattern to be sure it runs away from your house. Do this by filling the depression with water and watching the overflow. If necessary, dig a shallow channel to direct water away from buildings and toward the street.
  6. Direct your downspout or sump-pump outlet to your rain garden depression, either by digging a shallow channel or by piping runoff through a buried 4-inch, black-plastic drainpipe.
  7. Now you are ready to plant the native plants recommended in the designs on this page. Place taller plants in the center of design and shorter ones along the edges. Adjust plant numbers if your garden is larger or smaller.
  8. Put a 3-inch layer of untreated shredded hardwood mulch on bare soil around plants to conserve moisture and keep your design looking neat.
  9. Water the planting every other day for a few weeks or until it shows growth and good establishment.

Rain Garden Sample Layout

Diagram of layout for a rain garden


Clay soils

  1. False dragonhead
  2. Palm sedge
  3. Softstem bulrush
  4. Arrowhead
  5. Giant bur-reed
  6. Water canna
  7. Squarestem spike rush
  8. Southern blue flag
  9. Swamp milkweed
  10. River oats
  11. Cardinal flower


Well-drained to sandy soils

  1. Tussock sedge
  2. Marsh milkweed
  3. New England aster
  4. Sweet coneflower
  5. Lizard’s tail
  6. Buttonbush
  7. Shining blue star
  8. Riddell’s goldenrod
  9. Rose turtlehead
  10. River oats
  11. Blue lobelia