Pressing and Drying

Pressing and Drying

June 27, 2015

Pressing

In order to facilitate the storage and use of plant specimens, the procedure of pressing plants flat to be mounted on cardstock has arisen. When you are ready to press your plant, consider what you want the dried specimens to look like. All the “valuable information” has to be visible from a single side, since the other side will be glued to paper. Make sure both sides of the leaves are visible, and turn flowers/fruits in various directions so the fronts, sides, and backs of them are visible.

Long, slender plants can be folded in a zigzag fashion or clipped in strategic locations to fit inside the newspaper sheet. Bulky parts and fleshy fruits can often be halved or sliced before pressing. Odd fragments (bark or large hard fruits) should be kept in numbered or labeled envelopes or packets with the main specimen.

Building your own plant press:

Specimens are pressed in a plant press, which essentially consists of a rigid frame, cardboard, blotter paper and folded newspaper but can be as simple as an extra telephone directory! The objective of the plant press is to flatten and evenly dry the plant specimen so that it may best be mounted and preserved on a sheet of hard cardstock while still retaining its morphological characters. Plants properly pressed, dried, labeled, and mounted can be stored indefinitely as a record of the flora. The equipment is simple and can be improvised. You will need a plant press and newspaper to hold the specimens. Plant presses can be purchased* or improvised. A recent article was published in Journal of the Botanical Research Institute of Texas detailing the design for a field press—please find this article attached in the appendix.

To build a general plant press you will need:

• 2 pieces of board of equal size at least as large as a folded newspaper: 12" x 16" (boards with holes for ventilation or lattice frames are ideal)

• Pieces of corrugated cardboard as ventilators (the same size as the boards/frames)

• Absorbent paper (folded newspaper, paper towels, or blotter paper)

• Foam (optional)

• Newspaper

• Rope, belts, or webbing straps to hold press together OR several heavy books to weigh down the stack of pressed specimens.

When pressing, alternate layers thusly: cardboard, absorbent paper, folded newspaper with the plant pressed inside, absorbent paper, cardboard...etc. Place the stack between the two boards/frames. Tie the press tightly and evenly with ropes or straps.

Drying

After collection and pressing, the next step in preserving a specimen is to make sure that all the moisture is removed from the plant. Any moisture remaining in a collection can result in the eventual rotting of that specimen, rendering it useless for scientific purposes. In a herbarium, plants are dried in a forced-air plant drier that approaches temperatures of 100°C. Presses are placed in the drier in such a manner that the hot air can be blown up through the cardboard corrugates to help dry the plants more evenly. In modifying this for home use, plants can be kept in the press and stored in a hot and dry location, such as a sunny spot, attic, garage, or car trunk. Specimens that are not particularly fleshy usually dry within 5-7 days. You may need to replace the absorbent paper every few days for fleshier plants. Once all the water is removed, the plant will last indefinitely. Some plants will require more consideration when drying, such as cacti and other succulent plants. Particularly fleshy plants might best be preserved after being cut longitudinally or transversely, and inner tissue may need to be scooped out.

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