Mr. Smarty Plants loves easy questions and this is one. There is a plethora of information on rain gardens in Iowa. Using your favorite search engine, type in rain gardens Iowa. Iowa has produced an entire detailed manual on how to create a rain garden. Find it at http://www.iowaagriculture.gov/press/pdfs/RGManualOct09green.pdf. More information and a more extensive plant list are at the Iowa State University Extension. Your county extension office may be interested in your project and have more information for you. Some of the plants suggested in these documents are pictured below. They are all native to Iowa and are designed to have something blossoming from February to October. Click on the scientific name under each photo to learn why each may be valuable for your site and the wild life, such as birds and butterflies, that each attracts. Be sure to check on light requirements, whether sun, part shade, or shade and choose accordingly. Use our Combination Search to find other suitable options for Ohio.
Mr. Smarty Plants recommends using plants native to your area for the reasons listed here. He envisions a curriculum for students that includes why one uses native plants, why rain gardens are beneficial, and hands on experience in building and planting the garden. Some suppliers for native plants near you are listed here.
Congratulations on such a great educational and ecological project.