An extensive botanical reference library that’s a growing resource for documenting and doing research has been on the Iowa State University campus for more than one-and-a-half centuries.

The Ada Hayden Herbarium is home to nearly three-quarters of a million plant samples, according to curator Deb Lewis. She calls the herbarium a one-stop shop for studying Iowa’s native plants, as well as plants from all over the globe.

“A herbarium is a museum or collection of dried and pressed plants and dried fungi,” Lewis says, “just about anything under the old botanical umbrella.” Most of the herbarium’s holdings are plants that have been dried, pressed, labeled, attached to archival paper and stored for reference. Mounted and kept correctly, Lewis says they can last for centuries.

The massive collection on the Ames campus has grown in recent decades after absorbing the University of Iowa’s 220,000 specimens in 2004, as well as 50,000 more from the University of Northern Iowa last fall.

“Charles Bessey started the herbarium in 1870,” Lewis says. “We have specimens from around the world and from every continent. We have about 710,000 or so specimens here in the herbarium.”

The herbarium is housed in a complex of four adjacent interior rooms on the third floor of Bessey Hall. The samples are stored in about 250 large metal cabinets that are spread across the facility’s 4,300 square feet. It includes plants collected by some of ISU’s best-known scientists.

“We have specimens from folks who are very famous here on campus, many collected by Louis Pammel, also many collected by Ada Hayden,” Lewis says. “And then George Washington Carver was here, and we have specimens that he collected while he was here and added to the herbarium.”

The herbarium’s director, Professor Lynn Clark, says it’s bittersweet to grow due to other facilities closing, but centralizing the collections of the three Board of Regents institutions has benefits. Clark says ISU now has a sample of every known plant native to Iowa.