Also called tallgrass prairie, mesic prairie was common historically but is extremely rare today. This grassland community occurs on rich, moist, well-drained sites, usually on level or gently rolling glacial topography. The dominant plant is big bluestem (Andropogon gerardii). The grasses little bluestem (Andropogon scoparius), Indian grass (Sorghastrum nutans), needle grass (Hesperostipa spartea), prairie dropseed (Sporobolus heterolepis), and switch grass (Panicum virgatum) are also frequent. The forb layer is diverse in the number, size, and physiognomy of the species. Common taxa include the prairie docks (Silphium spp.), leadplant (Amorpha canescens), heath and smooth asters (Symphyotrichum ericoides and S. laeve), prairie coreopsis (Coreopsis palmata), prairie sunflower (Helianthus pauciflorus), rattlesnake-master (Eryngium yuccifolium), flowering spurge (Euphorbia corollata), bee-balm (Monarda fistulosa), prairie coneflower (Ratibida pinnata), and spiderwort (Tradescantia ohioensis).
At the time of European settlement it is estimated that there was over 800,000 acres of mesic prairie in southern Wisconsin. Today less than 100 acres of intact tallgrass prairie still exists, and is associated with other prairie communities, various wetland types, and oak openings. Mesic prairies are rare today because areas they once occupied have deep, rich soils built by the extensive root systems of the prairie plants, and have been converted to some of the most productive croplands in the world.