Growing Green: Rain gardens
It is that time of year when you should begin planning the gardens you want to plant this spring. A rain garden is the perfect garden to beautify your property and help the environment.
A rain garden is a planted depression in an area of lawn or soil that soaks up rainwater runoff from roofs, driveways, walkways and compacted lawn areas. It’s water that would otherwise carry pollutants directly to our streams. Rain gardens soak up 30 percent more water than an equivalent patch of lawn.
Stormwater runoff is water from rain or melting snow that “runs off” across the land instead of seeping in the ground.
Stormwater picks up many pollutants as it runs across our lawns, driveways and streets. These pollutants go directly into our streams and lakes, affecting our water quality and adding to floods. Flash flooding from stormwater runoff can cause property damage.
Pollutants such as fertilizers, pesticides, deicing salts, litter, antifreeze, grass clippings, pet waste, eroded soil and motor oil are carried into stormwater.
Rain gardens reduce runoff by capturing rainwater and allowing it to infiltrate back into the ground. They help to reduce flooding and remove pollutants, provide pollinator and wildlife habitat and beautify the neighborhood.
Choose an area where you want to soak up rainwater at least 10 feet from the house. Rain gardens can drain water from downspouts or catch water that drains off roads and walkways. Avoid areas over septic systems. Do not place a rain garden in areas that are consistently wet. Rain gardens should drain completely within 24 hours.
The size of a rain garden depends on the size of the roof or lawn areas to be drained, the type of soil on your site (how well it drains) and how deep you would like your garden to be.
Before you dig, call PA One Call (8-1-1) to locate underground utility lines.
Use string or garden hose to outline the shape. Oval shapes are best. Remove the turf. Dig the garden to the desired depth. Make sure the bottom is level.
Gardens on a slope require more digging to create a flat bottom. Use the extra soil to build a berm on the downhill side. Refill the depression with soil, adding compost or decayed leaves to loosen clay soils. Consider including an overflow outlet for unusually heavy rains.
Your rain garden will have areas that range from very wet to dry. Choose native plants suited for those areas and plant them close together. Observe your newly-dug rain garden after a storm to determine which areas stay wet the longest. Mark those areas with string or plant markers.
Plants on or near the berm will be dry most of the time. Plants with semi-evergreen leaves will help control erosion during the winter months. Choose plants with a variety of shapes, colors and bloom times to provide maximum pollinator and wildlife habitat. Top-dress with two inches of mulch to keep weeds out and moisture in.
Protect your investment by watering the plants as needed for the first season. Remove weeds as soon as you see them. For the following two years, continue to remove weeds as needed, replace plants that fail, and do not add more mulch.
“Growing Green” is contributed by Lehigh County Extension Office Staff and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-746-1970.