In brief, an herbarium is a collection of specimens of plants that have been pressed and dried, or, as we like to call them, dead flat plants. Even though an herbarium can be a huge museum collection and occupy a lot of space, without these rather uninspiring-looking specimens it is nothing. These dead flat plants are attached by gluing and often sewing onto a standard-sized piece of very high-quality, archival, heavy white cardstock 11.5" x 16.5" in size, along with the data about their collection (where, when, by whom, and details of the environment and the plant itself) and a little "packet" for loose material.
The specimen can be a complete plant, or even several small plants on the same sheet of cardstock—or, for larger plants like trees, it will be just a little bit of a branchlet. In any of these cases, we typically make specimens of plants that have flowers and/or fruits (in addition to leaves and stems or twigs), because these reproductive parts are very useful in studying plant classification and identifying species.
Specimens of this sort can last a surprisingly long time, as long as they are kept away from mold, insects, and natural disasters (including clumsy botanists). For example, we have nearly 600 specimens collected around New Braunfels in about 1850 by Ferdinand Lindheimer, the "Father of Texas Botany" (to see two examples, click here). Some older herbaria (that's the plural of "herbarium"), like those found in Europe, have specimens over 400 years old.
There are several thousand herbaria in the world, and they come in all sizes. Small herbaria of just a few hundred specimens can be very useful at a small park or for teaching. Research and university herbaria often have several tens or hundreds of thousands of specimens. Fewer than 100 herbaria in the world have over a million specimens, and the one at the University of Texas at Austin is one of these. The largest herbarium in the world is in Paris; it was founded in 1635 and has almost nine million specimens.
So what do we do it for? What good is an herbarium? There are many reasons, but the most important ones boil down to four. The specimens in the herbarium are used to:
- Study the classification and evolution of plants. Whether using a more old-fashioned, "traditional" approach that involves just comparing the gross features of the specimens, or applying the latest molecular techniques and sequencing the DNA, the specimens are an integral part of how the research is conducted.
- Study and document plant distribution: what plants grow where, and how their distributions may have changed over time. Terms such as "biodiversity inventory" and "flora" (see below) apply here.
- Develop better ways to identify plant species. There is a constant need to know "what plant is that?" by lots of different types of people—from private landowners and wildflower enthusiasts, to weed control personnel, writers of environmental impact statements, conservationists, biologists, public land managers, and many more.
- Conservation. It's hard to have effective plans for conservation of our plant resources if we don't know what they are. The herbarium and the knowledge it produces are essential tools in our efforts to save these resources and to chart the changes that have occurred and continue to develop.
As an example, one common product of an herbarium is called a "flora" (Point 2). A flora is a detailed inventory and description of all the plant species that grow in a given geographical area, and it can cover a tiny area (like a small park), a medium-sized area (a county, for instance) or a large area (all of Texas or even all of North America). Floras use all of the herbarium specimens from a given area amassed over years of collecting, plus new collections by the botanists involved in producing the flora, and apply to them all of the knowledge from years of study on plant classification (Point 1). The result, which is usually published as a book, but can also be a CD or a Web site, will usually include all the botanical details of the plants of that area. But more importantly, it will also provide ways to identify the plants (Point 3), pictures, and information on distribution, ecology, and rareness. A good "flora" for an area is one of the most basic tools for anyone working in plant conservation and ecological land management (Point 4).
You might ask: why not just go out and study the living plants in the field? Well, anyone doing any of the types of work mentioned above will do just that, and there's no replacement for that kind of information. But the herbarium provides something that going out into nature cannot: you can see specimens of all of the species you're interested in, collected over the past hundred years or more, in rainy years and dry years, spring and summer and fall, in flower and in fruit—all together in one place at one time. Add that to all the knowledge you can gain out in nature with the living plants, and you have a much better understanding of what's going on.
So, the herbarium may look a bit uninteresting—it is full, after all, of dead plants. But it is a place of great excitement. For some people, this excitement is because of the great age of a few of the specimens (hundreds of years old) and for others, it is due to the fact that each specimen has its own history of the efforts and dedication of the botanist who trekked to collect it. But most importantly, the collection is an essential tool in understanding and conserving the wonderful natural world around us, and there is nothing more exciting than that.