tree-logo.gif (7741 bytes) Plant Taxonomy (BIOL308)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321;;

Plant Collecting & Specimen Preparation

I.  Introduction
    As a part of most investigations, plant taxonomists often must collect specimens.  Specimens may range from and entire plant to a small fragment.  Reasons for collecting vary, though in most cases the purpose is to document the existence of a plant at a particular place at a particular time.  These specimens are called vouchers. 

II.  History   
lant collecting has been very important in the history.  It�s easy to forget, but plant collecting was one of the driving forces for the exploration of the earth. Remember Columbus? Or Captain Cook in New Zealand? The latter took along botanists on board ship to collect at different ports.

III.  Planning
To make a collection requires careful planning.  This is critical, especially if you're planning to do a good floristic study of a site (remember the 5 P's - Poor Planning Produces Poor Performance).  Before heading out to the field, prepare a list of equipment you'll need including plant press, collecting bags (plastic garbage bags work great) or vasculum, digging tools, clippers, notebook and pen, knife, coin envelopes, newsprint, hand lens, bottles, preserving fluid, literature (manuals, etc.). and maps.  A portable GPS device is an invaluable addition to the taxonomists tool bag. Learn about the plants likely to be on the site from herbarium labels. Especially, if you are looking for a particular plant. Don�t forget to check the weather conditions.  Also, check the preparedness of plants - are they flowering or in the appropriate stage of their life cycle?  You may need to obtain collecting permits in advance.   

    Botanical expeditions, especially to less developed regions of the world, can be dangerous - plan carefully. For example, not too long ago an entomologist was murdered on a collecting trip in Cambodia. In any event, know what you're getting yourself into (Daly article).

IV.  Rules for Collecting
erhaps the most important rule about collecting plants is: Don't extinct any populations! In other words, we don't want to throw out the baby with the bath water! The following is a series of guidelines adapted from the Plant Conservation Roundtable, Washington, DC; June 13 1986:

  1. Know which species are locally or nationally rare or protected.  Visit the MN DNR website for a listing of MN plants that are rare or endangered.  The terms endangered, threatened, special concern refer to plants that are near extinction, likely to become endangered, and likely to become threatened, respectively.

  2. Do not collect indiscriminately - just the minimum amount needed

  3. Avoid collecting from populations of fewer than 100 plants. A photo would have to do in this situation. Some suggest a 1-in-20 rule for collecting - meaning that no more than 5% of a population should be collected (Wagner, 1991). However, this may still be too many, especially in small populations (Pavlovic et al, 1991).

  4. If you encounter a plant with which you are unfamiliar, assume it is rare and: (a) if a small population and it is possible to return - photograph and collect only if it would add significantly to scientific knowledge; (b) if a small population and it is impossible to return - collect one specimen at most; (c) large population - follow the guidelines.

  5. When collecting multiple specimens for trade, etc., be sure that the plant is abundant enough to justify.

  6. Collect discreetly - avoid giving the general public the impression that it is acceptable to collect plants.

  7.  Avoid unnecessary damage to the site and/or plant especially if it is a tree/shrub.

  8. If you discover a new plant, notify appropriate officials.

  9. If you learn that rare or protected taxa may be destroyed, notify appropriate officials (i.e., Nature Conservancy, DNR)

  10. Care properly for any specimens collected.

V.  Selecting a specimen
     Plant material for a specimen should be selected carefully. 
When selecting a plant to study, your specimen should be representative of the population; i.e., pick a typical specimen. Avoid insect-damaged or otherwise atypical specimens. Your sample should show the range of variation of individuals at the site. Collect your specimen in flower and fruit and collect the entire plant if possible.  Be sure to collect rootstocks of herbaceous plants, rosettes of biennials.

    Many plants have certain critical features for identification purposes (see list provided in Radford, et al., 1974). Without theses features, the specimen may be very difficult, if not impossible, to identify. Become familiar with these features.  If the plants are small, collect several specimens.  And when documenting the flora of an area, be sure to collect plants of all sizes, not just those that nicely fit on herbarium sheets.  If collecting in a new area, try to collect in various habitats.

VI. Data Collection 
    After the specimen is collected, record your data in a field notebook; a specimen is scientifically worthless without adequate collection data.  The notebook should be hard bound, not loose-leaf. Use indelible ink. The electronic age has spawned alternative methods of recording notes.  For example, some use a laptop or hand-held computer, or dictate notes in a tape recorder in the field and transcribe them later.

    You should record the following information:  (a) your field number (all supplemental material will be given same number; (b) name of plant (if known); (c) locality (be precise; section-township-range; a GPS system is an excellent addition to the tool bag of any field botanist); (d) altitude; (e) habitat; (f) observations not apparent from the specimens, especially color [note: there are color charts to help standardize color terminology], abundance, odor, height of plant, etc.; (g) date; (h) ecological conditions at the site. Conclusion: the more data the better! This information will be used to prepare your herbarium labels (a specimen without a label is worthless).

VII.  Specimen Preparation
    There are three major methods of preparation. No matter which is selected, preserve collections soon after they are picked; specimen quality quickly deteriorates. If you can't, place specimens in a refrigerator until they are processed.

A. Quick-freeze
    Place plants in a freezer at low humidity. To prepare specimens, place it in a container in a freezer (-10 C). Best results are obtained with turgid (not wilted) and dry (no dew or other surface moisture) specimens and if the containers are not more than half full. Do not pack the specimens too tightly. Small containers are preferred to larger ones. I use one-pint Chinese take-away food containers and they work well.

    When ready to use, remove the specimens from the freezer and allow to thaw. Thawed specimens remain in good condition for a few hours. Re-freezing is generally not successful. Thus, it is important to keep the specimens frozen until they are used.  If the specimens are left long enough in the freezer and the container is not air-tight, water will sublime and the specimens will become freeze-dried. Although they are very brittle, freeze dried specimens don't "melt" like other frozen flowers and maintain their color and form.  One advantage of this technique is that it works great to preserve color, odor, and shape. Thus, this method is particularly well suited for classroom use. However, frozen specimens are bulky, require costly storage, and specimens "melt" when removed from the freezer.

B. Liquid preservation
    Simply place the specimen in a vessel containing some type of liquid preservative. These specimens will last indefinitely. This technique is good for succulents, fragile specimens and/or if want to maintain the integrity of floral parts such as with orchids. It is especially well suited for specimens intended for dissection and/or classroom demonstration. Liquid preservation is often necessary for some types of studies such as those for microscopic studies (i.e., chromosome counts).  However, this technique is more costly than the others (fluid and containers).  Other disadvantages include the odor and toxicity of the preservatives and the final specimens are more difficult to work with.  These specimens are also more bulky and weigh more. The specimens typically discolor and become brittle.

    Some common preservatives include: 50-70% EtOH; FAA - 90 mL EtOH (70%), conc. formalin (5 mL, glacial acetic acid (5 mL); ethanol and formalin mixtures; alcohol (11 parts) 40% formalin (1 part) glycerin (1 part) water (8 parts).  Check the MSDS and HMIS sheets ( when working with these materials.

C. Press and Dry (Herbarium specimens)
    This is the standard and most common method for preserving plants. To prepare a specimen prune the plant as necessary to obtain an attractive, yet scientifically accurate, specimen.  Then place the plant between newspaper. Be sure that some leaves face up and others face downward.  Arrange the plant is an attractive way. Large stems should be bent into a "V" or "W". A card with a slit can help hold plants in a bent shape. Plants shouldn't extend beyond edge of newspaper. Write your collection number on the outside edge of the newspaper. Some specimens are very difficult to fit into the press or cause special problems (e.g., succulents, thick woody structures; large; very small; spiny).

    Place your specimen in a plant press , which is essentially an old-fashioned "Dagwood Sandwich" comprised of blotters (also called dryers) and cardboards (also called ventilators).  Assemble the press in the following sequence:  frame � cardboard (note corrugations should all run in the same direction - perpendicular to the long axis of the press) - blotter - specimen in newsprint - blotter - cardboard - blotter - specimen � blotter � repeat, ad infinitum. Tighten press with strap. 

    Place the press over a source of heat with adequate ventilation.  Light bulbs work well and minimize the fire hazard.  Be sure that the heat source doesn't touch the plant material.  After 8-12 hours open press and rearrange as necessary. Press again. It may be necessary to change the newspaper and/or blotters. It is critical to dry specimens quickly to prevent decomposition, prevent mold growth, and maintain color.

    Specimens should be pressed immediately after they are picked.  If this is not possible, place the specimens in the refrigerator.  They will usually keep reasonably well. 

VIII.  Special techniques
Aquatic plants with lacy leaves are usually floated in a tray of water over a sheet of herbarium paper. The paper is gently lifted up and the excess water drains off. Cover with waxed paper and then place in press.  Succulents, woody plants, and large plants such as palms, require other techniques to make good specimens.

    Specimen packets, also called fragment folders or packets, may need to be prepared to place loose pieces of plants.  A simple packet can be folded from a standard sheet of paper by folding the bottom third up, the top third of the paper down and approximately an inch on either side backwards.

IX.  Labels
Once the specimen is prepared, a herbarium label must be complete and should include all pertinent information as described above (e.g., scientific name including genus, species, author citation, locality, habitat, date of collection, name of collector, collection number).  Labels are prepared from information in your field notebook. Do not abbreviate on the label.

X.  Ethical Issues and Collecting
     Believe it or not, even collecting has ethical issues to consider. For example, should the commercial sale of fossils be permitted? Many scientists say "no" because it leads to the loss of valuable data that will never be recovered, whereas commercial collectors believe that many of the specimens would go to waste if it were not for them finding them. Further, many museums buy from commercial collectors. Currently, vertebrate fossils are permitted to be collected on private land with a permit from the BLM. The permit is usually only given to museum collectors. Plants are not yet rare enough to warrant these discussions, but many similar issues exist. What do you think?

    Another important question is what to do with Native American artifacts, particularly human remains? Should these materials be reburied or is it acceptable for them to be studied and displayed in museums? A particularly tragic example is the plight of Ishi's brain (Bower, 2000).

XI. Web sites

XII. References

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Last updated:  09/29/2008 / � Copyright by SG Saupe