The cover image for our February issue shows a digitized herbarium specimen of flowering yellow trout lily plants (Erythronium americanum). This image relates to the article, Warmer temperatures are linked to widespread phenological mismatch among native and non-native forest plants, by Tara Miller et al., which is part of a special feature on Leveraging natural history collections to understand the impacts of global change. Here, Tara Miller and Lahari Indraganti tell us the story behind the image:

These flowering yellow trout lily plants (Erythronium americanum) were collected by Irene M. Storks in Grafton County, New Hampshire on May 16, 1974. The plants were preserved as an herbarium specimen and later digitized by the Hodgdon Herbarium of the University of New Hampshire. Images of digitized herbarium specimens, or pressed plant specimens, are available online. We used this specimen, and others, in our research by using the collection information to indicate that the species was flowering on May 16 in 1974 in New Hampshire.

Herbarium specimens have increasingly been digitized – meaning they are scanned and the images are made available online. These digitized specimens enable researchers to access and use them for research much more easily.

The use of herbarium specimens in phenology research – or the study of the timing of seasonal events – has grown exponentially over the last two decades. Researchers can collect data from specimens, including information on the timing of leaf out and flowering. For example, in our study, we examined pictures of digitized herbarium specimens, selected the ones which had early leaves (for tree species) or flowers (for shrub and wildflower species), and then compiled the information on where and when those plants were collected. We used this information as an estimate of peak leaf out or flowering timing, and compared that timing to historical temperature data. In this way, herbarium specimens have been used to study how leaf-out and flowering timing is changing with warming temperatures.

Below, Lahari Indraganti recounts her experience collecting and preserving herbarium specimens:

“When I first started working at a herbarium, I began by updating the species labels for plants in the collections. Looking at many specimens also allowed me to note details that would not preserve well on a specimen, like colors, odors, and textures. As I worked there longer, I was able to go on many collection trips with experienced botanists and learn from them.

For me, making sure not to damage any part of the plant will always be nerve-wrecking. You start pressing the plant by sandwiching it between pieces of absorbent paper and cardboard. How a plant is arranged at this stage is how it will dry and later be displayed. I feel great pressure to dry the plant in a way that will ensure people long into the future can see the unique and identifiable characteristics of the plant. I am also motivated by the desire to press the specimens in an aesthetically-pleasing manner. Collecting plants is a meticulous process that is as much an art as it is a science.

Once the specimen is dried, it needs to be arranged beautifully on a piece of archival paper and glued with an acid-free glue. Next, I make a label for the plant with the correct species identification and collection details, including location. To see my own specimens filed with specimens collected decades and sometimes centuries ago is a thrill that never gets old.”