The Lewis and Clark Expedition, also known as the Corps of Discovery, embarked on a monumental journey across the newly acquired western lands of the Louisiana Purchase from 1804 to 1806. Commissioned by President Thomas Jefferson, the expedition’s primary objective was to explore and map the vast North American interior, seeking a potential water route to the Pacific Ocean. A key part of this undertaking was to gather extensive information about the region’s natural resources, including its diverse plant life.
Botanical Mandate and Expedition Methodology
President Jefferson held a deep interest in botany, considering it among the most useful sciences. He instructed Meriwether Lewis to thoroughly document the flora of the newly explored regions, emphasizing plants with potential economic value, medicinal properties, or those that could contribute to agriculture. Prior to the expedition, Lewis received training in Philadelphia from Benjamin Smith Barton, a prominent botanist, learning how to properly collect, preserve, and label plant specimens.
The explorers meticulously recorded their observations in journals, detailing plant appearance, habitat, and local uses, often noting colors, aromas, and textures. They preserved specimens by pressing them between sheets of blotting paper and storing them in protective covers. Despite challenges like humidity and insects, this systematic approach ensured the plant collections provided a significant scientific record upon their return.
Key Plant Discoveries of the Expedition
The expedition documented approximately 178 to 240 plant species previously unknown to Western science, significantly expanding botanical knowledge of North America. Among these were several plants that proved culturally and economically important, often with uses learned from Indigenous communities.
One such plant was the Bitterroot (Lewisia rediviva), a low-growing perennial with a fleshy taproot and striking pink to white flowers. Indigenous tribes, including the Shoshone, Flathead, and Nez Perce, highly valued its bitter roots as a food source, often boiling them or mixing them with meat and berries. The plant’s scientific name, Lewisia rediviva, honors Meriwether Lewis and its ability to “revive” from a dried state.
Another notable discovery was Camas (Camassia quamash), a member of the lily family recognized by its grass-like leaves and vibrant blue flowers. The bulbs of the camas plant were a staple food for many Northwestern Indigenous peoples, including the Nez Perce, who cooked them in earthen kilns to convert starches into sugars, creating a sweet, nutritious food. The expedition members themselves consumed camas, sometimes to their digestive discomfort, highlighting its unfamiliarity to their diet.
The Ponderosa Pine (Pinus ponderosa) was also observed, a tall evergreen tree characterized by its long needles and cinnamon-colored bark that develops distinctive jigsaw-like pieces with age. Indigenous tribes utilized its inner bark as a food source during spring, a practice Lewis and Clark documented. The expedition also used the durable wood of these pines for constructing canoes, especially after crossing the Bitterroot Mountains.
The Golden Currant (Ribes aureum), an attractive shrub with bright yellow flowers and edible berries that ripen from yellow to black, also caught the explorers’ attention. Native American groups consumed these berries fresh or dried them for later use, sometimes mixing them with flour or dried meat to make pemmican. Lewis noted the ripening of these currants in his journals, recognizing their potential as a food source. The Osage Orange (Maclura pomifera), known for its strong wood used for bows by Indigenous peoples, was among the first plant specimens Lewis sent back east from St. Louis.
Impact of Their Botanical Findings
The botanical work of Lewis and Clark significantly contributed to the scientific understanding of North American flora. Their expedition returned with hundreds of plant specimens, with around 226 preserved plants currently housed in the Lewis and Clark Herbarium at the Academy of Natural Sciences in Philadelphia. These collections, along with their detailed journals, provided the first systematic record of many plant species in the American West.
Frederick Pursh, a German-American botanist, was instrumental in organizing and describing 124 of Lewis’s plant collections, publishing them in his 1814 work, Flora Americae Septentrionalis. This publication made the expedition’s botanical discoveries accessible to the wider scientific community, influencing subsequent botanical studies. The findings also offered valuable insights into the traditional ecological knowledge of Indigenous peoples and the diverse natural resources of the explored territories.