Soap Weed (Yucca)

Photo: Creative Commons 2.0, Matt Lavin

None of the Expedition’s writers ever mention the common yucca plant which they surely would have seen in the drier western prairies, on either side of the Continental Divide.

However, Meriwether Lewis, when describing Lemhi-Shoshone Indian dress, wrote about "a small cord of the silk-grass" which has interpreted by several scholars as referring to the yucca. Many Indian peoples pounded the hard leaves to loosen the fibers, which were twisted into thread.

Yucca has many practical purposes – Native people and Euro-American pioneers made an effective soap from the roots, thus it was often referred to as “soap weed.” Medicinally, the root was used to treat upset stomachs, arthritis, and inflammation (and still is today). The flowers, stalks, and seed pods can be eaten, when properly cooked.

It’s perplexing why Meriwether Lewis didn’t document the plant in his botany writings. Scientifically speaking, the plant (Yucca glauca) was not officially “discovered” until the English naturalists Thomas Nuttall and John Bradbury ascended the Missouri River with competing fur trading companies in 1811.

Yucca’s cream-colored, bell-shaped flowers attest to its membership in the lily family. The Dakota Indian name for it is Hupestula, Omahas, the Poncas call it Duwaduwa-hi, and Pawnees know it as Chakida-kahtsuor Chakila-kahtsu. Its needle-sharp leaves have given it the common name "Spanish bayonet.”