Capulin Volcano lies within a transition zone, from the high elevations of the Rocky Mountains to the sweeping grasslands of the Great Plains. The prevailing wind direction in this region is westerly. Once precipitation moving into the region reaches the grasslands, there is generally only enough water to support short (less than 2 feet) and medium-sized (2-4 feet) grasses. However, as the winds travel toward Capulin, they pick up more moisture and as a result deliver enough precipitation to support a few tall grass (over 5 feet) species.
Within the monument, shortgrass prairie is dominant. Medium- sized grasses, and the three main species of tall grasses (Big Bluestem, Indiangrass, and Switchgrass) are also present. Blue grama and Sideoats grama are two dominant grasses that thrive in the monument.