Manassas Journal Messenger | Rain gardens: help for wet yards

Is there a place in your yard that stays moist after it rains? Then you may want to consider building a rain garden.

A rain garden is the inverse of a raised bed garden: Instead of soil being built up, the bed is sunken a few inches below the level of the surrounding landscape. It gathers and holds rain water, allowing it to soak in slowly, instead of running off, or pooling in your yard’s low spot. It’s good for your drainage, and good for the environment.

Where to Position Your Rain Garden

Location is important. Water should flow across a grassy area (filter strip) before reaching the rain garden, and then flow out toward a storm drain or street. Be sure that the rain garden is at least 10 feet from your house’s foundation to prevent basement flooding. Don’t put a rain garden in the lowest spot of your yard. Locate it uphill, so that it intercepts the water before it reaches the low spot. Test drainage by digging a one foot deep hole. Fill it with water until saturated and then fill it again. If it doesn’t drain in 24 hours, the site is not suitable for a rain garden.

How to Build Your Rain Garden

Make the rain garden an oval or oblong area approximately 5 to 7 percent of the size of the area draining to it (roof, yard, etc.) – typically 150 to 400 square feet. Call Miss Utility at 1 (800) 552-7001 before you dig. This free service will mark the underground utilities in your yard, so you won’t dig near them.

• Prepare the soil: Remove at least six inches of soil to make a level bottom. Replace the soil to within three inches of the surrounding level. Use – or mix in – compost, sand, topsoil and other soil conditioners for better drainage. Mound the extra soil at the lower edge of the rain garden to make a berm or raised lip to further slow the water during a storm.

• Plant: Use shrubs and perennial flowers that tolerate extreme conditions – very wet as well as dry. Native plants do well in such conditions. Add mulch to protect plants. Pull weeds and water the garden until the plants are established. Keep the rain garden’s edges well defined to make the garden attractive.

Rain gardens imitate the spongy, absorbent forest floor that covered our land before development. Most of the water from rainstorms now falls on solid surfaces – like our roofs, driveways and roads. That storm water picks up pollutants, such as fertilizers, sediment, motor oil and pet waste and carries it through storm drains into local waterways and the Chesapeake Bay.

Rain gardens offer homeowners a great way to help filter out some of this pollution, while addressing a drainage problem in their own yards.

Many Web sites provide information and resources on rain gardens, such as the Virginia Department of Forestry at www.dof.virginia.gov/rfb/rain-gardens.shtml and www.raingardens.org.

Paige Thacker is a Horticulture Extension Agent for the Virginia Cooperative Extension and a member of the Local Environmental Education Partners.