For binding, tying, and lashing, cordage (rope) was made mostly from plant fibers. It was also the basic material for constructing baskets, mats, and clothing. Grasses were sometimes used for cordage, but most grasses in Nez Perce territory do not have strong fibers and so were only used for temporary purposes or in combination with other materials. Native grasses that grow in the Big Hole valley are: buckwheat (Erigonum umbellatum), foxtail barley (Hordeum jubatum),Idaho fescue (Festuca idahoensis), and mannagrass (Glyceria sp.). A few nonnative grasses that have made their way into the park include: intermediate wheatgrass (Agropyron intermedium), red fescue (Festuca rubra), Timothy (Phleum pretense), and wheat (Triticum sp.).
The predominant vegetation in sagebrush steppe areas of the park is a variation of sagebrush and short grasses. Stream channels may support a lush understory of willow and other riparian plants but will rapidly graduate to more arid species, particularly farther from the mountains.