A pleasant afternoon collecting plant samples last summer took an unexpected turn for CU Boulder botanist Dina Clark. An irritated deer protecting her fawn threatened to charge. Backing away from the stomping doe, Clark stumbled into a large patch of poison ivy and discovered, to her horror, “a sea of ticks” marching up her legs.

Collecting botanical samples can be fraught with a certain amount of drama. But then finding an elusive or unusual plant more than makes up for the effort.

Clark and Tim Hogan are collection managers for the herbarium, the botany division of CU’s Museum of Natural History. Clark’s botanical research takes her to the high plains, particularly the canyons of the Purgatoire River in southeastern Colorado, while Hogan often heads into the San Juan and Sangre de Cristo mountains.

“Getting out in the field is about more than just the flora,” Clark said. “It’s also about the nuance of the place. You begin to get a sense for where you’ll most likely find what you’re looking for. Every place has a distinctive flavor.”

Located in the basement of the Clare Small Building near the Recreation Center, the herbarium houses more than a half-million grasses, flowers, lichens and mosses. In what was formerly a women’s gym, rows of tall metal cabinets are filled with folders containing a wealth of specimens and critical information about them.

The botanical collections in the herbarium represent the most complete documentation of Colorado’s flora in the world. The herbarium also includes significant collections from western North America, the American Arctic and Alaska, the Altai and Caucasus Mountains of Central Asia and the Sierra Madre Occidental of Mexico.

This comprehensive collection is regarded as one of the most important natural history repositories in western North America. Its large store of lichens and mosses alone makes it notable among university herbaria, Hogan says.

The earliest botanical collections were gathered by CU Boulder faculty and researchers in the biology department, dating back to the early 1900s. Retired professor and botanist William Weber became curator of the herbarium in 1946 and substantially added to the collection over his 50-year tenure. He wrote a number of manuals identifying Colorado plants. The herbarium’s collection is named in his honor.

For archiving, the dried plants are glued onto paper with attached labels containing their scientific name, where and when they were collected, and information about the habitat where they were found. Each representative plant is known as a voucher specimen. The scientific value of a specimen hinges on the label.

The herbarium is a valuable resource for researchers who study plant vouchers collected through the years. The collections serve to document the distribution and abundance of particular species, and are essential to the understanding of evolutionary relationships. In addition, Clark pointed out, “We can’t predict how these specimens will be utilized in botanical research in the future. With DNA testing, we’re looking at relationships between plant families using specimens that were collected years ago.”

“Everything we know about biodiversity on the planet is housed in natural history museums and herbaria like this one,” Hogan said.

When Clark and Hogan go into the field, they try to document every plant that grows in a particular area. Floristic studies such as these do not pertain just to biological evolution, but also to cultural evolution. Some places where plants were collected are now buried under pavement, submerged by reservoirs or so degraded by human impacts that plants can no longer grow there. Plants collected before the habitat was lost serve as a crucial record of conditions now gone.

Every plant in the herbarium has a story to tell. While in the field searching for plants, botanists need to be a combination of sleuth, adventurer and patient observer to tease out the story and learn about the plant, biodiversity, the environment and the cultural climate of when it was collected. For example:

Aliciella sedifolia, a rare species of flowering plant, was thought extinct after it was collected in the late 1800s. The label of the original specimen indicated the plant was found on Sheep Mountain. The trouble was, there are many Sheep Mountains in Colorado. In 1995, the plant was rediscovered on Half Peak in the San Juan Mountains, and in 2007, a small population was found nearby on a Sheep Mountain now presumed to be the site of the original collection.

Poison hemlock—the so-called Blood of Socrates because it is the toxic plant the philosopher used to commit suicide—looks similar to the wild carrot and to osha, a medicinal plant found in the Southwest. Poison hemlock grows along roadsides and creek beds, and has caused many accidental deaths due to mistaken identification.

The herbarium is currently digitizing all of its specimens.

“Collections don’t grow obsolete,” Hogan said. “They grow more important over time as new techniques for studying the specimens are developed. I think of our collections as not just preserving science, but also preserving our stories and our cultural histories.”

The University of Colorado Museum of Natural History houses the largest natural history collection in the Rocky Mountains. More than 4 million objects are categorized into seven disciplines: anthropology, botany, diatoms, entomology, paleontology, invertebrates and vertebrates. The collections include the world's oldest documented Navajo textile, the Aiken bird collection and Colorado's largest collection of bees.

Learn more about the plant collection at the university herbarium website.

Learn more about the other collections at the Museum of Natural History website.