Procedures - Rare plant surveys

The Minnesota Biological Survey (MBS) conducts rare plant surveys primarily for vascular plants and has provided funding for limited moss and liverwort surveys.

MCBS botanist Karen Myhre searches for aquatic rare plants

MBS botanist Karen Myhre searches for aquatic rare plants. Photo by Carmen Converse


MBS plant surveys are conducted to:

  • document new locations of rare plants

  • document new county and state records for plants

  • provide confirmation of plants recorded in vegetation samples (relevés)

  • better understand the current distribution and abundance of plants in the state

1. Review of existing information

Prior to conducting field surveys for rare plants in a particular county or region, information is reviewed about the landscape and the plants that may be present. Some of the sources consulted are:

  • herbarium and historical records of plants (from theses records botanists and plant ecologists obtain information about habitat, associated species and native plant communities, field identification characteristics, time of year when species is most visible or in flower or fruit, etc.)

  • aerial photos, maps (such as wetland, soil, lake, topographic, etc.), and associated data to aid in locating targeted habitats

  • recommendations from other botanists, plant ecologists, local land managers, and other knowledgeable individuals

2. Selection of targeted plants and survey sites

Based on review of existing information, the rare plants likely to be present in the county or ecological unit are identified.

Sites and other habitats likely to contain areas of preferred habitat for the targeted plants are identified and a seasonal work plan is developed to optimize locating the targeted plants.

3. Field survey techniques

Botanists conduct field surveys for targeted plants mostly between late April and mid-September. Timing of searches for specific rare plants is determined primarily by the life history of the species (when does it flower or fruit?), with attention paid to variations in seasonal weather patterns.

Plant collections are made using standard herbarium procedures. A complete collection typically includes either flowers or fruit, and underground portions of the plant. Certain groups of plants have more specific collection guidelines (such as sedges and woody plants). When a rare plant population appears to be secure, a collection is made of all or part of the plant. For conservation purposes, the roots of rare species are often not collected and only the portion of the plant required to make positive identification is collected. Occasionally only a photographic record is made of a rare species if it is adequate for positive identification.

MCBS botanist Karen Myhre searches for aquatic rare plants

MCBS Botanist Karen Myhre presses plant specimens in the field.

The freshly collected specimen is placed within a sheet of folded newspaper with the leaves, flowers, etc, arranged in a natural position but clearly showing the diagnostic features. The sheet is placed between blotters and ventilators, then put in a press and compressed by tightening straps around the press. The press typically accommodates many plants. It is placed in a warm and dry environment soon after collections are pressed to ensure proper drying and preservation. After several days of drying, the plants are removed from the press and stored in a dry place until identification can be verified.

4. Information management

Data collected during plant surveys are recorded on field forms, in electronic data files, and as museum voucher specimens. After field surveys are completed:

  • The identification of collected plants is verified using plant keys and by consulting with other botanists. An archival quality label is prepared (including collector, date, location, etc.) and voucher specimens are deposited in the herbarium of the J. F. Bell Museum of Natural History at the University of Minnesota, where they receive final curation.

  • The specimen label information is recorded in the herbarium database. More detailed information related to rare plant collections is entered into Biotics in the Natural Heritage Information System (NHIS). Other plant collections provide confirmation of plants recorded in vegetation samples stored in the Relevé Database in the NHIS. All collections are used to update lists of documented plant species for each of Minnesota's counties (county records).

  • Botanists contribute information to evaluations of sites that are important for rare plants and native plant communities. These site evaluations are used to guide conservation activity, such as special management to protect rare species and native plant communities or acquisition as a park or natural area.

MBS State Botanist Welby Smith talks about Minnesota plants and the collection and management of botanical specimens.

Botanist welby Smith talks about collection and management of plant specimens. This slideshow requires the latest version of Adobe Flash Player.


a pressed herbarium specimen

Herbarium specimen of water-hyssop (Bacopa rotundifolia), a species of special concern in Minnesota.