Thinking at a higher level than plant communities, the state can be divided into broad ecoregions that share certain characteristics of soil, vegetation, and hydrology.
Perhaps the best resource on Indiana’s ecoregions is The Natural Heritage of Indiana (1997), edited by Marion T. Jackson. In a series of essays by professional botanists and ecologists, the book systematically covers every ecoregion in Indiana, along with with its native flora and fauna, aiming to tell us what Indiana once was, what it is now, and what it promises to be.
Reproduced in the book is a favorite map of natural regions developed by state botanist Mike Homoya, available as a poster from the Indiana Academy of Science. An outline of the map with a key to regions is presented here: Natural Regions Map
The Environmental Protection Agency has developed an interactive map of Indiana ecoregions. This is intended to assist gardeners by specifying the type, quality, and quantity of environmental resources as well as similarity of climate. For example, most people in central Indiana live on “loamy high-lime till plains” in Zone 5a.
You can enter your zip code to learn about your hardiness zone, ecoregion, frost dates, and current drought conditions.