Kentucky Bluegrass

Human settlement can change the countryside beyond recognition

The rolling hills centered at Lexington, Kentucky south of Cincinnati, the oldest settled part of the state, and known for horse breeding, are called the Bluegrass Region. This area, through which the Kentucky River flows, is underlain by limestone, which forms a soil excellent for grasses. It is an example of a countryside transformed by human occupation, far different from what the Shawnees inhabited.

The grass common in American lawns and pastures that is called Kentucky bluegrass is actually an Old World grass, Poa pratensis, that possibly arrived in this country as hayloft sweepings saved for planting pasture. My authority for this is Field Crops by Howard C. Rather (New York: McGraw-Hill, 1942), pages 4 and 124. Although there are native American grasses, cultivated grasses are mostly from Europe and Asia. As in England, much of the American countryside is man-made country, quite different from what it was less than 200 years ago. Where I was brought up, in the Midwest, there is no remnant of the dark, unending hardwood forest that extended from Pennsylvania to Illinois (a forest reserve in Western Pennsylvania claims to be a remnant). This observation applies not only to the forest regions of the midwest that are now farming land, but much besides. The treeless prairies west of the Mississippi were kept treeless by regular autumn fires in the dry, tall grass. In my own region, the Wyoming hills are now covered with sagebrush and tumbleweed, not the lush grass that attracted cattlemen in the 1880's, and which they destroyed by overgrazing. When the grass is gone on the short-grass prairie, it never comes back. An area in far southwestern New Mexico illustrates this strikingly. It is an area, near Hachita, that for some reason was never grazed, and is still covered by waving grass. All the surrounding country is dry, sandy desert covered with coarse plants. The hardwood forests of northern New Hampshire, for example those around Conway, were totally destroyed, and all that you see now is recent growth. The southern yellow pine that now grows there looks nothing like what met the 18th century settlers.

Bluegrass is an important pasture plant. Canada bluegrass thrives with less nitrogen. Kentucky bluegrass can then be planted after the soil is improved by fertilization or growing of legumes. Bluegrass is also rotated with tobacco to help the soil recover. The grasses turn brown with hot, dry weather, says Rather, so it is best as spring pasture. My lawn certainly reflects this. Irrigation through the summer keeps the grass green on lawns. All our lawns, coast to coast (with some exceptions in the South) have their ancestors in Britain. White clover often accompanies bluegrass, usually appearing without seeding, and is also excellent grazing, although it too requires water. However, it does not root deeply or resist drought well enough to really provide enough nitrogen, so alfalfa, sweet clover, or red clover are required for this purpose. Bluegrass resists close grazing (or mowing), driving out other grasses under these conditions. It grows rapidly enough in the spring to force out white clover, then the white clover prospers later.

Return to Geology Index

Composed by J. B. Calvert
Created 19 May 1999 Last revised 18 August 2002