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Bessey's Locoweed

Photo of Bessey's Locoweed.

Bessey's Locoweed

Oxytropis besseyi

by Kathy Lloyd, Montana Native Plant Society

Exactly when Meriwether Lewis collected specimens of Bessey's locoweed (Oxytropis besseyi) is not entirely clear. That he did collect them is certain. There are two specimen sheets containing samples of Bessey's locoweed in the Lewis & Clark Herbarium in Philadelphia today. The first sheet bears a label written by the botanist Frederick Pursh that reads, " Near the head of Clarks River Jul. 1806." This sheet was among those discovered at the American Philosophical Society in 1896, after having been presumed lost. The second sheet containing specimens of Bessey's locoweed has an interesting history as well. Frederick Pursh must have taken these specimens with him when he traveled to London. Following Pursh's death in 1820, they ended up in the herbarium of his patron, A. B. Lambert. They remained there until Lambert's death in 1842, when they were put up for auction with his other herbarium collections. Fortunately for us, an American named Edward Tuckerman was at the auction and bought most of the Lewis and Clark specimens. He eventually donated the collection to the Academy of Natural Sciences where it was joined with the other Lewis and Clark specimens into today's Lewis & Clark Herbarium. This second specimen sheet also contains the type collection of Oxytropis lambertii, which are not Lewis and Clark specimens and are attributed to Bradbury. The label applied by Frederick Pursh to this sheet says, "Oxytropis argentata Head of Clarcks river. July 1806." Oxytropis argentata was the name applied to the species by Pursh; the name was later changed to Oxytropis besseyi.

In early July Lewis and his small party traveled from Traveler's Rest on Lolo Creek near present-day Missoula, along the Blackfoot River and over today's Lewis & Clark Pass. Several dates have been suggested as the collection date. Some authors believe it was collected on July 1 or 2 near Traveler's Rest, and others think it was collected on July 6, 1806 when Lewis collected other plant specimens with purple flowers and divided leaves. The label information is very similar to that given for fern-leaf lousewort, collected on July 6 on the Blackfoot River in Powell County. Regardless of exactly when it was collected, Bessey's locoweed was undoubtedly collected in Montana and is a plant of special historical significance. Lewis, in his journal entry for July 6, 1806 writes, "river bottoms narrow and country thickly timbered. Cottonwood and pine grow intermixed in the river bottoms musquitoes extreemely troublesome. we expect to meet with the Minnetares and are therefore much on our guard both day and night. the bois rague [red osier dogwood] in blume. - saw the common small blue flag [Rocky Mountain iris] and peppergrass. the southern wood and two other speceis of shrub are common in the prarie of knobs. preserved specemines of them." Lewis pressed the shrubs American silverberry (Elaeagnus commutata), shrubby cinquefoil (Dasiphora fruticosa) and bitterbrush (Purshia tridentata), as well as the purple-flowered fern-leaf lousewort (Pedicularis cystopteridifolia) and elephanthead pedicularis (Pedicularis groenlandica) on July 6. If he also pressed Bessey's locoweed on that day, he was indeed a busy man.

Bessey's locoweed is a very attractive plant. A member of the pea family (Fabaceae), Bessey's locoweed, also called Bessey's crazyweed, is a perennial with a stout taproot and compound basal leaves that usually have seven to 21 pinnately arranged leaflets. The plant has a silvery appearance due to the long, straight, soft hairs that are found on the leaflets. The flowering racemes have from five to 30 flowers that are reddish-purple when young. They fade to blue as the flowers age. The keel petal has a short beak and the calyx is covered with stiff hairs. The seeds are brown and sometimes have purple spots.

Oxytropis comes from the Greek oxys, meaning sharp, and tropis, meaning keel, referring to the beaked keel petal common to Oxytropis species. Bessey's locoweed is named for the botanist and taxonomist Charles E. Bessey.

Bessey's locoweed is found from Alberta and Saskatchewan, where it is rare, to Nevada and Colorado, where it is also rare. Look for it on gravel benches and streamsides from the prairies to the foothills. It is a colorful addition to the flora of Montana's plains and prairies.

Bessey's locoweed makes an attractive addition to xeric and native landscape plantings. The plant is adapted to our variable climate and is drought-tolerant. Seeds may be hard to find in commercial quantities, but can easily be collected. When collecting seeds, be sure you are on land where such activities are allowed and be sure of identification.

Whether you grow Bessey's locoweed in your garden or admire it on Montana's prairies and foothills, remember its special place in Montana and botanical history and help preserve its native habitat.