According to its vegetation map, about a third of the park (14,586 acres) is covered in grasslands. There are many different grassland plant associations within this group, sometimes with very different species compositions and appearances. Some of the park's grasslands have high shrub cover, as much as 25 percent.
Among the most fascinating of the park's grasslands are those dominated by the grass called curlyleaf muhly (Muhlenbergia setifolia). According to the vegetation map report, these "give the mid-elevation slopes their distinctive character and are part of what sets the landscape of the park apart from most others in the Southwest."
Curlyleaf muhly is a grass that occurs almost entirely in the Chihuahuan Desert, but even here it is uncommon. The park vegetation map reportly noted that while similar curlyleaf muhly-dominated communities are found occasionally throughout the range, none are known to dominate their respective landscapes as those in the park do. These associations are among the newly described plant associations for the park.
The grass family is prominently represented on the park's plant list, with 135 known species. Some of them are non-native, a few of those are invasive, damaging species, but most are native.
See the park's plant list for details on grass species.