The predominant naturally-occurring vegetation on the Monument is composed of the sagebrush steppe plant communities once common to much of the intermountain region of southern Idaho.
These shrub steppe communities include a dominant shrub, often sagebrush, interspersed with open, sparsely vegetated areas of grasses and forbs.
The steep slopes of the Monument’s bluffs west of the Snake River provide an environment that contributes to the diversity of plant species. In addition, a riparian zone and localized wetlands occur along the Reservoir.
Livestock grazing prior to establishment of the Monument in 1988 also undoubtedly contributed to alteration of soils, loss of native grasses, and establishment of non-native plant species.
Non-native plant species known to be present include Russian olive (Eleagnus angustifolia), Russian thistle (Salsola kali), quackgrass (Agropyron repens), cheat grass (Bromus tectorum), blue mustard (Chorispora tenella), tansymustard (Descurainia sophia), tumble-mustard (Sisymbrium altissimum), and medusa head (Taeniatherum caput-medusae).
These and other non-native species likely to be present, compete with the Monument's native plant communities, disrupting ecosystem processes.