Thank you to all who attended our December 6th LIISMA Partners Meeting and Plant Pressing Workshop! At this interactive event, participants were instructed by botanist, Daniel Atha, on the applications and techniques for creating museum quality herbarium specimens. Participants practiced pressing fresh plants and mounted dried specimens with Daniel’s guidance.
Plant pressing aims to translate three-dimensional subjects into a two-dimensional space as a preserved object to create museum specimens for preservation, science, research and art. Daniel began with an introduction to plant pressing, likening our modern techniques to those of ancient Egyptians. For thousands of years, humans have sought to preserve biological materials through the ages, and many rules hold true today. Like mummies housed in pyramids, plant specimens need to be preserved in a space without sunlight, which would degrade color over time and reduce the fidelity of the specimen to its live counterpart. Like live plants, preserved plants are also vulnerable to damage from insects and fungi. This is why it is critical to thoroughly dry specimens in a plant press for at least 24 hours and to mount specimens with special considerations to seal off access for insects. Plant framers typically glue paper on the back of their frames to keep insects out.
Preserving a plant in posterity begins in the field at the time of specimen collection. This is a critical time to record all information needed to identify the plant and display with the mounted specimen. It is important to select the most representative sample and collect ethically by avoiding the harvest of vulnerable species. This may mean only collecting one specimen when there are several at the site, and avoiding harvest of threatened or endangered plants without authorization. Ask yourself these questions when collecting a plant in the field, and be sure to record data in your field notebook.
- Required information: Who collected the specimen? Where was it collected? When was the specimen collected (time and date)?
- Additional information: What are the plant characteristics while it is alive? What color are the flowers, if any? Are there any pollinators or insects visiting, and which? What is the surrounding habitat type? What is the fragrance of the plant? Is there any taste?
It is necessary to record any information that you won’t be able to glean from a preserved specimen removed from its environment. Recording visually apparent plant characteristics, such as leaf toothing, is not necessary at this stage since the pressed specimen will still display these traits. If a species identification is assigned to the plant, it is necessary to do so while in the field, not retrospectively with the sample. All field botanists can benefit from this method, as our field notes are more reliable than memory!
While we take advantage of plant presses, our plant pressing predecessors utilized a vasculum – a tin case that housed specimens in the field, but not without causing damage to leaves, flowers, or seeds, and even contaminating one sample with another. While using plant presses minimizes disturbance, the challenge remains of getting the plants in the field safely to the plant press. This is why Daniel recommends bringing the plant press to the plant in the field. Within the press, the sample would be placed into newspaper and blotting paper nestled into corrugated cardboard. This enables moisture to leave the sample quickly as it is compressed. As you lay the plant sample into the newspaper, take care to flatten out materials into a two-dimensional form. You may want to bring tweezers to gently arrange leaves, or gently press down on foliage to secure its shape as the rigid cell walls are compressed. A standard plant press is 12 in. x 18 in. to follow the widely used 11.5 in. x 16.5 in. standard mounting paper, which is slightly smaller than the press to prevent overhang. If a sample is too large for this standard size, the collector must think creatively to determine how to best display the plant segmented across multiple sheets, or delicately fold the plant to conform to the size of the press to fit on one herbarium sheet.
After nesting the sample gently into newspaper and cardboard within the press, Daniel recommends tightening the straps thoroughly by standing on top of the press to ensure it is as compressed as possible. After tightening the press, the specimen will be thoroughly dried in as little as 24 hours! Daniel’s setup entails leaving the press atop two small space heating fans for 24 hours to dry the specimen as efficiently as possible. You can also forgo the fan, but your plants won’t be dry for two to four weeks. After the drying period, plants are ready to mount!
To begin the process of mounting, plants are placed onto mounting paper to determine the desired arrangement, with space left in the bottom right for the label. Next, place the plant on a sheet of newspaper with the back side facing up and drizzle glue across the plant. Carefully pick the plant up and place it in the desired location on the mounting paper, leaving room in the bottom right for the label. For more delicate specimens that are prone to being weighed down or damaged by excessive glue, Daniel suggests the “butter knife technique.” This entails laying the specimen on the mounting paper in its desired position and directly applying glue under the plant with a butter or palette knife.
After either gluing method, use a moist rag to gently press down on the specimen to ensure it adheres to the paper and to remove any excess glue. There may be parts of the plant that don’t adhere right away or didn’t get enough glue; for these, use the palette knife to add additional glue under the plant where it didn’t initially stick. For woody plants, sew thick stems or branches to the mounting paper and tape over the knot on the backside. Next, overlay wax paper on the sample and place small weights, such as grommets, on the paper to ensure the plant adheres to the paper. After the glue dries, your plant is fully mounted and ready for framing!
Special thanks to Daniel Atha for sharing his knowledge of plant pressing! To learn more, check out the recording of Daniel Atha’s demonstration at our workshop.
