VII. Pressing Specimens
When the plant is pressed for preservation, it needs to be laid out to dry in a way that fits an herbarium sheet and allows full examination of reproductive and vegetative characteristics.
Some tips for pressing and drying your plants:
- Specimens should be pressed and dried within 24-48 hours of collection to prevent both wilting and mold. Ideally, press specimens as soon as possible after collecting.
- Press specimens in the plant press you check out in lab, which is composed of 2 external wooden frames, corrugated cardboard stiffeners, blotter sheets (to absorb moisture), newspaper (to hold specimens), and straps to hold the press together tightly.
- Each specimen should be pressed in a sheet of newspaper that is labeled with the collector’s name and collector number assigned to the specimen in your field notebook. Write this information on the outside of the newspaper so that it can be read without disturbing the specimen! Newspaper may need to be trimmed to the appropriate size before using.
- Each specimen should be arranged as naturally as possible in the press. Strive to clearly illustrate the diagnostic features of the specimen. Avoid excessive overlapping of plant parts. This may require selective trimming of your specimen, such as trimming leaves or splitting stems. If you must trim leaves to increase visibility of other parts of the plant, leave the petiole so that an observer will know that a leaf was once there.
- Large specimens that do not fit in the press need to be folded so that all parts of the plant fit in the press. Do this by slightly breaking the stem and arranging the plant in a “V”, “N”, or “W” shape depending on the length of the specimen. Any parts of a specimen that protrude from the press will not be adequately preserved.
- Try to arrange leaves so that both surfaces are visible. Large leaves can be folded to show both sides. Inflorescences and flowers often need to be spread out to reveal important parts. Consider pressing some flowers open, some closed, and some split to show internal structures.
- Bulky parts, such as roots or bulbs, can be split longitudinally in order to fit in the press.
- Nothing (plant material or newspaper) should be sticking out past the edges of the wooden frame of the plant press.
- Once placed in a press, specimens should be placed on edge in the plant-drying oven. Press straps may need to be tightened as the specimens shrink from evaporation. Plants typically dry in 1-4 days depending on the type of plant.
