The Great Plains of North America is one of the largest expanses of grassland in the world. It extends westward from the deciduous forest of the Appalachian mountains to the foothills of the Rocky Mountains and southward from Canada to Mexico.
The east-to-west gradient of increasing altitude, decreasing precipitation, and increasing temperature and the north-to-south gradient of temperature and humidity have created zones of tall, medium, and short-grass prairies. This vast prairie region is comprised chiefly of warm-season grasses which tolerate the climatic extremes.
Tall Grass Prairie
Historically, the tall-grass prairie consisted of big and little bluestem, switchgrass, and Indiangrass. These species thrive in zones of 30-40 inch annual precipitation and reach 6-8 feet in height. Within this zone, cordgrass (Stipa spp.) and reed grass (Phragmites spp.) are dominant species in the wet lands. Thousands of years of tall grass dominance (owing to managed and natural fires preventing forest development) created a rich, fertile soil which now characterizes the corn belt of the USA.
Medium Grass Prairies
The mixed grass prairies found in the 20-30 inch rainfall belt represented a transition zone comprised of a mixture of tall, medium, and short grasses (US Precipitation Map). Medium height species included little bluestem (Schizachyrium scoparium), side oats gramma (Bouteloua curtipendula), and dropseed (Sporobolus spp.). These grasses reached a height of 3-5 feet.
Short Grass Prairies
The short grass prairies found in the 15-25 inch annual precipitation zone are dominated by blue grama (Bouteloua gracilis) and buffalograss (Buchloe dactyloides). This semiarid climate zone extends from central Nebraska westward to the Rockies, and from Texas to Saskatchewan.
The major tall-grass prairies of the Midwest and Great Plains were quite overwhelming to early settlers. Tall-grass prairies have been described as oceans, and some found them too vast to cross. After the American Revolution, settlers and pioneers waited almost 40 years (1840-1880) before settling 700 million acres of bountiful prairies.
Without large numbers of domesticated animals and plows the tall-grasses seem too massive to control. Pioneers felt more comfortable with trees and felt land that grew only grass was inferior. They mistakenly reasoned that if there wasn't enough rain for trees, then there wouldn't be enough rain for crops. They avoided the "Great American Desert." Some historians felt that the Native Americans of the prairies were more feared than Native Americans of the woodlands and this feeling contributed to the slow acquisition of the prairies.
Other practical factors entered into the matter: few navigable rivers, the different prairie soil did not respond to the plows available, few railroads extended into the prairie, settlers often did not own enough horses and mules, and few available trees for building homes, fences, tools and fuel. So, much of the tall-grass prairies was given away. But with a poor understanding of the growth habits of prairie grasses, and the inability to predict the response of these grasses to overgrazing, immense areas of the medium and tall grass prairie regions were seriously degraded within 50 years. Medium grass prairies often reverted to short-grass prairies because the latter grasses were more tolerant to intensive defoliation.
The terms tall-grass and short-grass typically refer to native range species, all of which are perennial types. Introduced species that are now very common, such as perennial ryegrass or tall fescue, vary widely with respect to height. Some are suited for turf while others for forage purposes. Therefore, the tall-grass and short-grass terms are used in more of a historical sense.