Although individual grasses sprout almost anywhere there is soil, grasses at Craters of the Moon are most commonly found as the understory (plants that grow beneath) of sagebrush steppe. Grasses play an important role in the ecosystem by stabilizing soil, helping hold moisture, and providing forage for wildlife.
Most grasses fit into two groups: bunch or sod-forming. With the exception of cheatgrass (Bromus tectorum), an annual European sod-forming grass accidentally introduced to the United States in the 1800s, Craters has almost exclusively native bunch grasses. Bunch grasses are classic desert plants that occur in scattered clumps. This type of growth pattern reduces competition for the limited soil nutrients and water available here. The principal grasses found at Craters include bluebunch wheatgrass (Elymus spicatus), Sandberg bluegrass (Poa secunda), needle grasses (Stipa spp.), Idaho fescue (Festuca idahoensis), and Great Basin wildrye (Elymus cinereus). These grasses are a vital part of a sagebrush steppe ecosystem that provides habitat for a variety of mammals and birds. Native grasses are a key component of successful rangeland fire rehabilitation, and in healthy communities they can provide resistance to invasive weeds.