by Ellen Dean
In natural history museums around the world are collections of dead plants that are curated by scientists called plant taxonomists. These collections are known as herbaria (in the plural) – a single collection is called an herbarium. If you go to see a bug museum, you say you are going to an entomology museum. If you go see the collection of dead plants, you say you are going to the HERBARIUM! This is generally confusing, because the name makes people think that it is a collection of living herbs – like oregano. But no, it is dead and flattened plants.
A flattened plant is an excellent representation of its living three-dimensional counterpart, and once glued onto sturdy archival paper, it becomes a herbarium specimen that can last for centuries (the oldest specimens are about 500 years old). Each specimen has a label that details who collected the plant and where and when they collected it. The label can provide all sorts of information about the habitat where the plant was collected, the elevation where it was found, the height of the plant, the color of the flowers, or whatever else the collector noted down.
Herbarium specimens can provide information on flower shape, leaf shape, leaf arrangement, seed structure, pollen structure… and much more! They can even be used as a source of DNA for sequence analysis. Plus, because the specimen label provides detailed information on when and where the plant was collected, herbarium specimens are an historical record of where and when plant species have grown. They are the basis of much of the information that is published on plant species in floras and guide books.
While herbarium specimens are not as beautiful as living plants, dead specimens do not need to be watered, fertilized, or repotted. They also take up less space than living plants. The largest herbarium in the United States has over 8 million specimens! The herbarium at UC Davis as over 350,000 specimens and is a very busy place. It is housed in a museum called the Center for Plant Diversity. Herbarium staff identify plants for the California Animal Health and Food Safety Laboratory, as well as Farm Advisors, and Master Gardeners around the state.
Anyone can use the herbarium. Students and faculty with many types of research projects bring in plant samples for identification. Some students are looking at changes in grasslands or forests in various parts of California, others are studying the variation in just one type of plant or are looking at insect-plant relationships. Vegetation ecologists who work for the state of California and the California Native Plant Society use the herbarium to identify plants that they collect at their study sites; by putting accurate identifications on their plant samples, their vegetation data is much more accurate. Consulting botanists from many different companies use the herbarium to familiarize themselves with the rare plants of particular areas before they do field surveys. The herbarium’s staff and students have also been involved in many projects to provide plant lists for parks and reserves throughout northern California (available on the herbarium website http://herbarium.ucdavis.edu/plantlistsandfloras.html).
People often ask how the herbarium was compiled – where did the specimens come from? Many of the specimens were donated by researchers associated with UC Davis. Wild and cultivated tomato specimens were collected by tomato breeders in South America and wine grape specimens collected throughout the world by wine grape breeders. Valuable high elevation and high latitude specimens were collected by the eminent vegetation ecologist Jack Major. The specimens he collected while describing the vegetation of his high elevation study sites represent species that will be greatly affected by climate change, and they will be a valuable record of how those areas looked fifty years ago. Specimens were also donated by the California Native Plant Society Vegetation Program; those specimens represent species they assessed in the Sierra Nevada foothills. The herbarium is a valuable record of the research that has taken place in California and continues to be a valuable resource for the botanists of today.
The herbarium also trains students in curation and plant identification, including a herbarium plant collecting internship and a herbarium internship. In most years, a dozen or so paid student assistants work in the herbarium. One of the current undergraduate assistants at the herbarium, Mai Xong, has become interested in our collection of Hmong culinary and medicinal herbs – a collection that was made as part of two research projects at UC Davis. Mai is of Hmong heritage and has helped us label and mount some of the specimens, and now she has been inspired to make a plant collection of her own in her mother’s garden. Mayra Huerta, another undergraduate assistant, is assisting with a herbarium specimen-based study of two species that grow in Mexico and Central America. Are they one species or two? A simple, but complex question that she will answer by making detailed morphological measurements on dozens of specimens.
So, if you need help with a plant identification, you know where you can find help! The herbarium website is easy to find: http://herbarium.ucdavis.edu.