More than 400 plant species grow in the 410 acres of Chiwaukeee prairie. The diversity is partially a response to abrupt gradation from wet prairie to mesic and dry-mesic prairies, a characteristic of the dune and swale topography formed with the lowering, in stages, of glacial Lake Chicago. This has resulted in wet and dry conditions in close proximity. The wet swales, rich in calcium minerals, support some species, called “calciphiles”, that only grow in such a mineral-rich environment. Dry-mesic prairies occupy the former beach dunes.