Rain gardens offer homeowners the chance to do their part in lowering storm water pollution by creating water-retaining and filtering, flora-filled swales in their yards. A single 10-feet by 12-feet rain garden can effectively filter 30,000 gallons of roof runoff water a year, thus preventing that water from picking up surface pollution and carrying that pollution to local lakes and streams. If you're considering adding a rain garden to your property, here is what you should know about soil type and plant selection.

Don't Worry So Much About Your Soil Type

Many people with clay-like soil assume that installing a rain garden on their property would require the digging up and replacing of dirt. These people fear that, since the gardens are designed to collect water, building them on slow-draining soil types will create areas of standing water and mosquito problems.

This isn't true. As long as you fill your garden up with plenty of native vegetation, you can catch and filter nearly 100 percent of your roof runoff water, regardless of the soil composition of your yard. Your local plant species are adapted to deal with your local soil types. If you live in an area with plenty of clay, then the plants in your area have roots that are capable of penetrating clay and soaking up the water within it.

Make Plant Selection Easier By Dividing Your Garden Into Moisture Zones

If you think of your rain garden as one big moisture zone, you're going to have a hard time finding plants for it. Why? In periods of heavy rain, the soil is going to be really wet since the garden is designed to have all of your roof runoff channeled to it. Because it's also designed to soak up that water fast, though, the soil on the garden's slope and the soil around the garden is going to be really dry during extended periods of no rain. To deal with this problem, divide your rain garden up into moisture zones.

The Ponding Area. The bottom of your rain garden is a ponding area -- it will be exposed to water during all rainstorms, and therefore, the soil in it will have a lot of moisture most of the time. The correct types of plants for this portion of your rain garden are obligate wetland plants. These are plants that are usually only found in wetland areas. They love saturated soil and can tolerate periods of flooding.

The Slopes. The sloped sides of your rain garden will get a good soak during heavy rains but won't retain much moisture during light rains or periods of no rain. For this section of your garden, you'll want to plant facultative plants. These plants are plants that can be found both in and outside of your local wetland regions. While they prefer damp soil, they're very hearty and can survive both periods of flooding and drought.

The Berm. The berm (the outside perimeter) of your rain garden will be its driest section. For this moisture zone, you'll want facultative upland plants. Facultative upland plants are plants that are normally found outside of your native wetlands but occasionally within the wetlands. They prefer dry soil but can tolerate moderately wet soil once in a while.

The key to a successful rain garden relies not on soil type, but on choosing the correct native plant species to occupy the soil type you have. You want plants that are going to soak up plenty of water but won't die in the process of doing so. Since the type of plants that are considered obligate wetland plants, facultative plants, and facultative upland plants vary by your region and climate zone, contact a local landscaping specialist from a company like Master Landscape to help you choose the right plants for each moisture zone in your rain garden.