The Friesner Herbarium is a collection of over 100,000 dried, pressed and preserved plant specimens. The Herbarium, third largest in the state, grew out of the personal collections of Dr. Ray C. Friesner, Professor and Chair of the Botany Department from 1920-1952. Since then, the collection has been contributed to by many Butler students and faculty.

The Friesner Herbarium's collections focus on the plants of Indiana, but include specimens from around the world. The collection has samples of 96% of the approximately 2500 taxa of native Indiana plants. Multiple specimens are present for most plants, providing more information than single drawings or photographs from books to assist in learning what a plant looks like. Most of the collections were made during the first half of the century and now constitute documentation of Indiana’s historical vegetation. They also provide information on the habitat (e.g., woods, swamp, prairie) where plants were collected and would likely be found again.