Artemisia cana Pursh, Fl. Amer. Sept.: 521. Dec (sero) 1813. (Asteraceae) - silver sage, Coaltown sagebrush. PH-LC 19, PH-LC 20, PH-LC 21 and PH-LC 22. PH-LC 19 was collected near the mouth of the Cheyenne River in Stanley Co., South Dakota, on 1 Oct 1804; the remaining sheets were collected above the mouth of the Cheyenne River near the Sully-Potter Co. line, South Dakota, on 2 Oct 1804. Synonymy: Seriphidium canum (Pursh) W. A. Weber
The term "sagebrush" is synonymous with the American West. What few visitors realize, and this was true of both Meriwether Lewis and William Clark, is that there are several different kinds of sagebrush in the West, and especially along the route taken by Lewis and Clark. To observe the differences among the species often requires a hand lens and a good nose. Most experienced workers with sagebrushes, and this includes many ranchers, recognize the various species simply by smelling crushed leaves. For the most part the different species difference in their overall shape and general appearance but this too requires study and experience. Some of the species are easy to recognize either because they different from other species by easily observed morphological features, or because of where they occur. On the northern Great Plains south of Fort Mandan along the Missouri River there is only a single species, the silver sage or Coaltown sagebrush, Artemisia cana. For more on the western sagebrushes seen by Lewis and Clark, see this page.
Artemisia cana is a large, freely branching shrub that is greenish-white in color when seen from afar, although the intensity of the color fades in the fall of the year. Unlike most of the western sagebrushes, the leaves of this species are deciduous so that they fall away leaving a rather bare looking shrub in the dead of winter. The flowers are tiny but numerous and form in long, dense spikes in late summer or early fall on newly grown branches. As sagebrushes belong the sunflower family (Asteracae) the flowers are in head-like clusters; there are 5 to 15 flowers in each cluster. Unlike some sagebrushes, all of the flowers have both stamens and ovaries so that each is capable of producing a single fruit termed an achene. The most distinctive feature of Artemisia cana is its entire, non-toothed or -cleft leaves. All of the other western sagebrushes have apically toothed or deeply cleft leaf-blades.
The species is widely distributed on the Great Plains from southern Saskatchewan to Nebraska and Colorado where it is common. To the west, the species occurs with less frequency in southern Idaho and southeastern Oregon southward into northern Nevada, and in scattered location in Utah south to northern Arizona. In California and western Nevada there is a variant that occurs mainly in the Sierra Nevada.
Lewis and Clark were greatly impressed by the shrub. They noted that pronghorn grazed the plant and that it was common on the high bluffs overlooking the Missouri River. That is true even today. Lewis uncharacteristically gathered several specimens of silver sage so that today there are four herbarium sheets in the Lewis and Clark Herbarium. The specimen gathered on the first of October in 1804 near the mouth of the Cheyenne River in Stanley Co., South Dakota, is now considered the "lectotype." This is a technical nomenclature term meaning that this sheet was selected by a botanist to be the one specimen used by Frederick Pursh to establish the name Artemisia cana. As may be seen Pursh annotated the sheet and it also has its original Lewis label. Unfortunately, this was not a wise choice as this sheet remained in Philadelphia while Pursh took to London two fragments of the collection made by Lewis on October 2nd. As this was the material he had at hand when he wrote Flora americae septentrionalis, this would have been a more logical lectotype. The rules of nomenclature say that whomever declares a lectotype must be followed and so Lewis first collection is and must remain the basis for Pursh's name.
The photographs by James L. Reveal were taken for The Academy of Natural Sciences in Philadelphia as part of the Save America's Treasures Program of the National Park Service, the National Trust for Historical Preservation, and the Institute for Museum and Library Services to protect the priceless specimens found by Meriwether Lewis and William Clark. In the spring of 2003, a book by A. Scott Earle and Reveal entitled Lewis and Clark's Green World: The Expedition and its Plants will be published by Farcountry Press. A CD-ROM containing images of the Lewis and Clark Herbarium Specimens along with detailed information about the collection is available. For additional images see The Lewis and Clark Herbarium - The Plants Seen and Collected by Lewis and Clark. For background information on the collections, see the Lewis and Clark web site at The Academy. For information on all aspects of the Lewis and Clark Expedition, see Discovering Lewis & Clark.
For more information on the nomenclature and identification of the specimens contact Dr. James L. Reveal at jr19@umail.umd.edu
For more information on the Lewis and Clark Herbarium contact Dr. Richard M. McCourt at mccourt@acnatsci.org
All images are copyrighted and their use, for any purpose, requires written approval.
