Now for the fun part – selecting your plants. Keep in mind that your rain garden, unlike a water garden, will be dry most of the time. The plants you select should be able to tolerate short periods of inundation, but not require constant, high moisture. Plants that are more moisture tolerant should be placed in the bottom of your garden. Plants which thrive in average or low moisture conditions should be placed further up in the garden, such as the side slopes.
To select plants, we suggest visiting a cool site sponsored by the Cincinnati Zoo and Botanical gardens at http://www.plantplaces.com/. Here you can search for different plans by color, bloom time, sun vs. shade, size and more.
How many plants you need will depend on the types of plant you select, however, as a rule of thumb, divide the size of garden by 2.25 to figure out how many plants are needed if placed on 18-inch centers. Don’t worry about exact numbers though – the garden should look however you want it to look.
Native species – that is, plant species that were present in this area before people were – are recommended because they thrive in local conditions, have deep root systems, and many tolerate both spring rains and summer drought. Once they’re established, they’re low maintenance.
For detailed information about native plants, including plant description, bloom times, sun/shade preference, growing height and more, check out Marvin’s Organic Gardens (Lebanon, OH) online list of native plants. Note that not all plants on this list are suitable for rain gardens.