Herbaria

When I am out walking, I often see plants that I would like to be able to identify, but I do not know their names.  Knowing a common name, or a genus and species, can provide you with a starting point for finding out lots more information about the plant, the habitat it lives in, and other species it has relationships with.

A herbarium refers to both a collection of plants and a place to store that collection.  Plants are mounted and labeled, and are accompanied by a data card providing information used for their scientific study.  Mountings may include whole plants or individual parts of a plant such as roots, flowers, stems, leaves, seeds, and fruit.  The data for each plant includes collector names, collection dates and locations, plant and habitat descriptions, and the condition of the specimen.

Specimen sheets are stored individually.  Plant parts that cannot be pressed flat including nuts, cones, fruit, and branches are optionally stored in jars filled with a preservative.  Historically, the preservative used was formaldehyde, but that was found to be harmful to humans as well as the specimens.  The standard for today’s museums is to use Carosafe, a non-flammable alcohol solution.  Another option is  70% ethanol, a flammable solution that must be used with extreme care.  Some sheets can be found in protective cases allowing a specimen to be herbicided, disinfected, or frozen to prevent contamination and deterioration from undesirable organisms or unfavorable environmental conditions.

Herbaria preserve a historical record of vegetation changes in small and large habitats.  Many plants that have become extinct either locally or world-wide are held in herbarium collections.  The associated data kept for each specimen provides a record of the plant’s original distribution.  Environmental science is using this data to track climate changes and identify how the loss of each species affects the original  community it lived in.

seeds pictured include dandelion, aloe, coast sandalwood, dill, and milkweed

Herbaria often serve as a repository for several collection types.  Collections of rare plant parts, fruits and seeds in particular, are used in the study of plant taxonomy.  Voucher specimens, another collection type, are plant samples with collection data kept in publicly accessible collections for long-term study.   Plant classifications are constantly updated.  Vouchers are used to authenticate the plant’s taxonomy and identify the location and habitat it was growing in at the time it was collected.

Herbaria are an excellent source of plant DNA, a nucleic acid that carries genetic information about the species.  DNA is widely used to study the evolution of a species and to identify close family relationships to other species.  Many older specimens collected over the past several hundred years can provide insights into the historical changes in vegetation over time for a specific location, aiding in geographic distribution studies.

There are several herbaria in the Chicago area that are easy to explore online.  Take a look at the Jurica-Suchy Nature Museum at Benedictine University’s collections, available online at: https://www.gbif.org/dataset/d39570b9-2972-4dbb-b41f-6826823176ae.  For a deep dive into what herbaria are and how they may be used, an article on specimen storage can be read at: https://www.nps.gov/museum/publications/conserveogram/11-12.pdf.  Also, a good reference book to consider is: Herbarium: The Quest to Preserve & Classify the World’s Plants, by Barbara M. Thiers.