Everyone needs a rain garden

Barb Mrgich
Adams County Master Gardener

Consider for a moment, the following questions. When we get a heavy rain, do you end up with standing water in your lawn? Or do you find you have a small river temporarily running through your yard? In either case your best solution to these situations is to plant a rain garden. A rain garden is designed specifically to drink up lots of water so that your standing water disappears or you interrupt and eliminate the flow of your "temporary river".

Even if you don't have a standing water problem, a rain garden can be placed to catch the water coming out of your roof gutters. One inch of rain on every 1000 square foot of roof yields 623 gallons of water. The average yearly rainfall in our area is about 42 inches. Thatís a lot of storm water.

Storm water runs down your gutters and across your lawn picking up pollutants as it goes. A rain garden located at least ten feet from the house will temporarily capture that water. Then, while it slowly moves through the garden soil, pollutants are filtered out by the extensive root systems of the plants. It stops the water from flowing onto neighboring properties or carrying pollutants to a nearby stream, river or lake. Are you aware that Adams County is part of the Chesapeake Bay watershed? The water that flows off our property eventually ends up in the bay. We need to help stop the flow of pollutants that are killing the bay. Think about how much clean, filtered water could go back into our water table if we each were to plant a rain garden.

Think of a rain garden as a bowl that will hold the water that flows into it until the special plants you have put in it absorb that water or the water has filtered back into the aquifer deep beneath your garden. From the surface, it won't look like a bowl because, after removing several inches of our typical hard clay, you will have leveled it with a big helping of compost or good garden soil. The clay that lives under most of our Adams County lawns is nearly impervious to water. You need to replace it with soil which will allow more infiltration.

A rain garden can't be made up of just any plants. It needs plants with deep roots that can handle a lot of water. It needs plants that can grow in occasional standing water, in normally damp soil, and still sometimes handle dry soil. All these criteria point to our native Pennsylvania plants.

Native plants are the ones that grew here before the European settlers arrived on our shores. Our natives evolved over thousands of years and adapted themselves to our soil and growing conditions. Their deep roots are able to break through our typically hard, clay soil. Since they evolved along streams and river banks, they adapted themselves to growing in constantly damp soil --- something that would rot the roots of many other plants.

Because you initially dig down about 6 - 10 inches to make the center of your rain garden a little deeper in order to hold water, you will end up with three zones in your garden. These include the center wet zone which may stay wet for up to two days following a heavy rain, a moist zone which makes up most of the garden, and a dry zone, or "berm". The berm is the outer edge which is built up to keep the water in the bowl. Native ornamental grasses are often recommended for the berm.

Special planning is needed before selecting the native plants for your rain garden. First, like any garden, you need to know how much sun or shade the plants will receive, the pH of your soil, and how wet or dry the soil will tend to be.

Your rain garden can be made up of perennials, large shrubs, trees, or ornamental grasses. Perennials will establish themselves quickly and give you a nice garden the first year. Trees and shrubs take longer to establish, but once mature will require the least maintenance and usually absorb the most water. Of course, you can combine all types of plants in the same garden but, as a general rule, keep the number of your plant selections to a minimum. Many native shrubs reproduce by sending out stolons, or underground runners, which will grow into a new shrub filling in the garden naturally. Likewise, many perennials will reseed themselves and pop up in different places within the garden. This is all good because the more concentrated the root system of your garden, the more water it will be able to filter.

Native plants are not always easy to find in our local garden centers. However, with more interest and demand for them, the selections are getting better. Also, mail-order sites and some Native Plant nurseries are available. For specific information about constructing your rain garden, visit our Extension Office at 670 Old Gettysburg Road. While there, you can also pick up suggested plant lists. When shopping for plants, read the plant tag carefully. It is the botanical name that tells you, for instance, if a viburnum is native or Asian. The native plant will always perform better in the rain garden, plus it will support our native wildlife and supply food for the birds.

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