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The Morton Arboretum’s Herbarium houses more than 187,000 vascular plant specimens, 17,000 lichens, and 1,300 bryophytes, many from Illinois and Missouri.

Its primary emphasis is on woody plants, both cultivated and spontaneous. It is a major resource to researchers in botany, genetics, conservation ecology, restoration, and other disciplines.

Plants of the Chicago region

One of the herbarium’s important collections vouchers the flora of the Chicago region. The region consists of 24 counties, five in Wisconsin, seven in Indiana, one in Michigan, and 11 in Illinois.

More than 2,500 taxa are recorded from this area and have representatives in the herbarium from each of the counties in which they occur. This herbarium collection is the database for Swink and Wilhelm’s Plants of the Chicago Region (4th edition, 1994). The Arboretum has the most complete collection of dried plants for this rich and diverse flora, which are included in vPlants, a virtual herbarium of Chicago-region plants.

The Arboretum’s herbarium contains several other important collections:

  • More than 20,000 specimens collected by Erwin Evert, author of Vascular Plants of the Greater Yellowstone Area, from the area of Yellowstone National Park and the surrounding mountains in Wyoming, Montana, and Idaho.
  • Most of the collection of Gerould Wilhelm, author of Plants of the Pensacola Region, from the western panhandle of Florida and southern counties in Alabama.
  • A portion of the plants collected in the early 1900s by E. J. Palmer, noted collector and botanist.
  • The vouchers of the genus Vauquelinia on which William J. Hess based a monograph.
  • Vouchers of the genera Nolina and southwestern Yucca that William J. Hess studied for the Flora of North America project.
  • The vouchers of the plants collected in the United States for the National Cancer Institute’s program to test plants for anti-AIDS and anti-cancer properties.