Rain gardens are a low area of a garden where runoff water is collected and slowly allowed to seep into the ground rather than flowing through storm drains. Many urban and suburban areas have encouraged their residents to plant their own rain garden using native plants to help replenish depleted underground aquifers. Rain gardens are designed to collect excess nutrients and pollution from the surrounding area before they reach the water supply. This means fast-growing, robust plants are needed to help purify the water.
Switchgrass, scientific name Panicum virgatum, is an excellent choice for a rain gardens in Illinois. This is a tall-growing prairie grass that reaches four feet high and up to two feet in diameter as the stalks of grass start to lean over. The individual stalks arise from a central clump and are about three feet long. They have a whitish waxy coating and are a metallic lavender to blue color that fades to a dry yellow-orange at the end of the season in the fall. The typically shaped grass seed heads are reddish-brown. They like moist soil and can tolerate flooding.
Leadplant, scientific name Amorpha canescens, is a perennial shrub plant that grows in close association with prairie grasses. It is a legume, so it is excellent at fixing nitrogen in the soil, making the nutrients usable by other plants. This is beneficial in rain gardens where waste water settles and seeps into the ground.
Leadplant reaches three feet high with reddish-purple racemes of flowers on the tips of the stems. The leaves are grayish-green colored and the entire plant is covered with fine white hairs.
Showy goldenrod, scientific name Solidago speciosa, is an herbaceous perennial shrub that puts on a bright yellow floral display in August and September. The pyramid-shaped flower stalks attract birds, bees and butterflies. The plant reaches three to six feet tall and prefers full sun to part shade. It usually thrives in dry sandy soil, but can tolerate the wet conditions in a rain garden. It is a great plant that easily will survive the dry season when the rain garden is not full of water.