Making Voucher Specimens

Voucher specimens are an easy way to document the occurrence and spread of invasive plants. When vouchers are stored in a herbarium collection, they become a permanent record of a species occurrence at a certain place and a certain time. A little time spent on making a good voucher can mean the difference between having a permanent scientific record, or just a piece of dead plant.

If you follow a few simple steps, you will be able to create a usable voucher:

  1. Collect an identifiable specimen.
    Usually this means collecting a piece of the plant with a portion of the stem, leaves, and either flowers or fruits. Seedlings, isolated leaves, and solitary fruits are usually not enough to identify the plant with confidence. If you can collect the whole plant, in flower or fruit, your specimens should be identifiable.
  2. Press and dry the specimen.
    Most herbarium specimens are preserved by pressing and drying. Specimens preserved this was can last for hundreds of years and are easy to store and study. Scientists press their specimens between sheets of corrugated cardboard under gentle heat, but you can press specimens in folds of newspaper, just be sure that they dry rapidly or they might rot. Specimens that are juicy or thick-skinned may be harder to dry and you may have to change the newspaper often to blot away all the moisture. In the U.S., most herbaria standardize the size of a herbarium specimen to 11" X 16", so, if you can fit your specimen in a fold of newspaper the specimen size will be fine. If your specimen is larger, try cutting it into smaller pieces that will each fit into a fold of newspaper.
  3. Make a permanent label.
    A good label is essential for a scientific specimen. A good label will have data on:
    • a.) Where the plant was collected. This allows others to check on the status and spread of the species. Include the name of the county, township, and a description of the locality. It is often useful to say how far the site is from some conspicuous landmark, like a river, post office, or train station. If you have a GPS reciever, include the longitude, latitude, and altitude.
    • b.) The habitat where the plant grows.
    • c.) The abundance of the species.
    • d.) The day the plant was collected.
    • e.) The name of the collector.
    You can also include:
    • f.) Descriptive data on the plant. Preserved specimens usually lose their color and texture, so notes describing the living plant can be very useful.
    • g.) Your field number. If you will be collecting many specimens, you may find it useful to keep a permanent set of field notes where your collections are sequentially numbered
    Most labels are 3-4" tall and 4-6" wide and are printed on good paper with permanent ink. Be careful! Most ballpoint pen inks are not permanent.
  4. Send the specimen to an established herbarium.
    Place your specimen in a box or padded envelope, with a few pieces of stiff cardboard to keep it from getting bent. If you mark the envelope as 'Scientific Specimen: no commercial value' you can send it through the Post Office by Library Rate. Most colleges, museums, and botanical gardens have herbaria that will accept good, properly labeled specimens. The Invasive Plant Council requests that you send your vouchers to the Brooklyn Botanic Garden Herbarium at the following address:

    Kerry Barringer
    Brooklyn Botanic Garden Herbarium
    1000 Washington Avenue
    Brooklyn, NY 11225-1099

    The Brooklyn Botanical Garden(BBG) will keep the IPC informed of the vouchers they receive. Be sure to let BBG know if you want BBG to acknowledge receipt of your specimens and include a return address. Also, BBG specimens are included in the New York Flora Atlas

    5. If you also wish to submit a voucher specimen to a local herbarium, simply prepare one specimen for BBG and one specimen for the local herbarium.

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