Scotts Bluff National Monument - Grasses

Scotts Bluff National Monument by National Parks Service

There are six recognized grasslands in the United States . They are the California grasslands, Intermountain grasslands, Desert grasslands, Shortgrass prairie, Mixed prairie, and the Tallgrass prairie. Scotts Bluff National Monument is located in the mixed or mixed-grass prairie. The most common grasses of the Monument include sideoats grama, needleandthread, prairie sandreed, and western wheatgrass. These are all native grasses, but there are also two very common non-native grasses - smooth brome and downy brome.

Grasses are classified into two different groups - cool season and warm season. The cool season grasses are the first to green-up in the early spring, because they grow their best during the coolest part of the growing season. On the other hand, the warm season grasses grow best in the hottest and driest part of the summer. The grasses of the Monument are of both kinds, and that is what you would expect. As the cool season grasses complete their growing cycle of flowering and then "going to seed," the warm season grasses take over. As they are actively growing, the cool season grasses are dying back and turning brown. This cycle of active growing keeps an abundant supply of green and nutritious food for the prairie grazers and seedeaters.

Most native prairie grasses are perennials. That is to say that they live for several years to decades. Their strength is in their root system which can be several feet deep. Young grass plants put most of their growth energy into developing their root systems first and then their leaves. This is advantageous to their survival. Usually the grasses will have more biomass below ground than above, and the root systems usually penetrate deeper into the soil than the leaves are high above ground. These are all advantages to growing in areas of low and irregular precipitation. Another advantage of an extensive root system is that the grasses can survive heavy grazing, because their growth areas are at the surface of the ground, not at the tips of leaves, like other plants. As grazing animals bite or tear off the grass leaves, new leaves will sprout from the roots. Finally an extensive root system protects the grasses from prairie fires. Fire may burn their leaves above ground, but the grasses will soon sprout new leaves from their root systems.