Grasses grow throughout Arches. Individual grasses sprout almost anywhere there is soil. Grasslands form in areas where wind-blown sediment and erosion have created a layer of soil that is several feet thick. Small grasslands form in potholes that have filled with dirt. Most desert grasses can be fit into two groups: bunch and sod-forming.

Bunch grasses are classic desert plants that occur in scattered clumps. This growth pattern reduces competition for limited soil nutrients and water. Indian ricegrass and needle-and-thread are bunch grasses. The relatively large ricegrass seeds are rich in protein and were an important source of food for Native Americans. Needle-and-thread has a sharp seed attached to a wound “thread” that drives the seed into the ground as it unwinds. Both of these grasses are perennial, becoming dormant during droughts. Ricegrass plants have been known to live over 100 years.

Sod forming grasses are what most people have in their yards. Galleta and blue grama are sod-forming perennials native to Arches, and usually grow together. Unlike most desert grasses, galleta can withstand heavy grazing and is important forage for bighorn sheep and mule deer. The seed head of blue grama looks like eyelashes.

Cheatgrass is a sod-forming grass that was accidentally brought to the United States in the 1800s. This European annual is now established throughout the west and frequently takes over areas disturbed by fire or livestock grazing.