What is a herbarium?

A herbarium is a museum for plants. Plant specimens are collected, dried, and preserved for study in an organized fashion not unlike a library.

Herbarium specimens provide data on the morphology, distribution, and growth and reproduction of plants.

Collection data associated with plant specimens can provide a detailed record of historical change. For example, herbarium specimens at ARIZ have been used to document the plant species that once occurred in the Tucson basin when the human population was only a tiny fraction of what it is today and the Santa Cruz River flowed year round; many of these species have vanished from our region (Mauz 2002).

Such information, preserved in specimens at herbaria such as ARIZ, will become increasingly important as a baseline for understanding the effects of global climate change

on plants and plant communities.

Plant specimens, housed in herbaria such as ARIZ, are used by researchers to:

  • describe new species
  • study the relationships among plant species
  • update the names and classifications plant species as our knowledge of their relationships changes
  • prepare identification guides (such as field guides and floras)
  • document plant distributions (e.g., for field guides and floras)
  • assemble plant checklists for parks, counties, state and other regions

Who uses a herbarium?

Scientists use the herbarium to conduct original research on plants. Such research ranges from discovering and describing new species, to preparing identification guides and distribution maps, to documenting the occurence of rare and endangered species. Herbarium specimens are the primary source of data for studying evolutionary relationships among plants belonging to particular groups (e.g., grasses, cacti, pines, oaks). In addition to providing information on morphology, herbarium specimens can be used as a source of DNA material for molecular analyses.

An important additional role of herbaria in scientific research is as a repository for vouchers: specimens that document the identity of species sampled or recorded in ecological, ethnobotanical, or pharmacological studies--to name just a few examples.

Students use the herbarium for class projects and for research related to plants.

Public Agencies such as the Park Service, BLM, and the State of Arizona use the herbarium to identify and inventory plants for management purposes and to monitor new introductions (i.e. invasive weeds) to the state.

Forensic Botanists and Law Enforcement Agencies use the herbarium to identify plants that are involved in legal cases (e.g., endangered species, plants that are the source of rugs, plants that help identify the scene of the crime).

Arizona Poison Control uses the herbarium to identify plants in cases of suspected poisoning.

Horticulturists use the herbarium to identify plants that grow well in gardens and to search for related plants that might do as well.

Homeowners use the herbarium to identify weeds as well as desirable plants in their backyards, for advice on what species to plant, and for help in identifying rare plants.