A Prairie Imperative—Part 1

July 1, 1993

StoryImage( ‘/Images/Story//Auto-img-11285416684393.jpg’, ”, ‘Percentage of each county in Illinois that was prairie in 1820. (Source: Louis R. Iverson, et al. 1989. Forest Resources of Illinois. An atlas and an analysis of spatial and temporal trends. Illinois Natural History Survey Special Publications No. 11, Champaign, Illinois.)’);

The Grand Prairie region of central Illinois is almost all farmland. From my home in Urbana, the nearest natural prairie is 26 miles to the north, a 5-acre remnant in a pioneer cemetery. When I take a trip to Pecatonica, I pass within 23 miles of a 5-acre piece of prairie in a cemetery east of Bloomington. Along my route from Urbana to Pecatonica, these are the two closest patches of prairie on the south side of the Illinois River.

After I cross the river and continue north, prairie remnants are not so far between. A few lie west of the highway in the wet, sandy plain of the Green River Lowland. Farther north, I approach the rocky prairies that are scattered across the Rock River Hill Country.

For the past year, I have been conducting a systematic search for prairies and other natural areas in the Pecatonica River Valley. Soon after I began this project, Sue Merchant told me about the Pecatonica Ridge, and she described its approximate location. I immediately looked for it on a set of aerial photographs and a topographic map, but I couldn’t find it. Then Sue took me to the prairie, and I learned why I didn’t spot it. Based on all that I knew up until then, I never would have suspected that the prairie would be where it actually is. Here’s why:

Native Illinois prairie has been almost entirely converted to farmland. Most of the remaining prairie is on soil that is too wet, dry, sandy, rocky, or steep to be farmed. Nearly all of the prairie that somehow escaped the plow has long been pastured—and prolonged grazing by livestock destroys prairie as surely as plowing does. Native grassland also needs to be burned periodically, or else it is overwhelmed by foreign grasses and invasive woody plants. Now most prairie remnants are growing up with brush and weeds because they do not burn often enough, if at all.

If a patch of upland prairie is to survive anywhere in Illinois—and if it’s not in an old cemetery or along a railroad line—it is likely to be on thin, rocky or sandy soil. It’s also likely to be on a steep, dry, exposed, south or west-facing slope. Under such conditions, the prairie is bared to the full effect of the summer sun during the hottest time of the day, and the vegetation feels the drying impact of southerly and westerly winds. In this harsh environment, native prairie plants sometimes manage to persist and out-compete foreign grasses, weeds, and invasive trees and shrubs.

The Pecatonica Ridge Prairie does not fit these circumstances. Although the prairie has thin, rocky soil, it’s not on a steep, high, exposed ridge that faces south or west. Instead, the Pecatonica Ridge Prairie is on the crest and slopes of a low hillside that faces north. Most importantly—and the reason why I passed over it while scrutinizing aerial photography: the prairie is next to a farmstead. I know that such areas have invariably served as pastures and have suffered about a century and a half of damage by cattle, horses, and even pigs. Never in my experience has an Illinois prairie survived prolonged and intensive pasturage.

The Pecatonica Ridge Prairie proved my assumptions wrong. As Sue Merchant and I later learned, the prairie was once a pasture, but it was not grazed too hard. Although the farmstead and barnlot were right across a fence, the prairie was at the south end of an 80-acre tract, and it had no water. A windmill pumped water beside a marsh at the north end of the property, a quarter mile away. Livestock must have congregated in the lush lowland down by the water, leaving the rocky prairie high and dry and pretty much unharmed.

It takes an extraordinary combination of good fortunes to allow a prairie to persist into the 21st century in Illinois. Yet these miracles do happen. In the case of the Pecatonica Ridge Prairie, it was a combination of three factors: (1) an unusual physical environment (thin, rocky, limestone soil that favors native prairie plants), (2) a fluke in land use and local geography (a pasture without a water supply), and (3) ultimately and most importantly, landowners who saw and appreciated the beauty and rarity of the prairie flowers—and who intentionally kept the prairie safe in recent years.

When I visited the Pecatonica Ridge Prairie with Sue, we came across four of my favorite plants. Here’s why I find them fascinating:

Porcupine grass

Porcupine grass grows on the thinnest, driest soil at the Pecatonica Ridge Prairie. It’s a characteristic plant of the northern Great Plains—more at home in the Black Hills than in the tall-grass prairie east of the Mississippi River.

The grass got its name because its seed has a needle-sharp point at one end and a 3-inch bristle at the other. When the seed falls to the ground, the bristle makes a right-angle bend and catches against vegetation; this serves to brace the seed and anchor it against the soil. Then the seed plants itself. The bristle twists in one direction when it’s moist (on a dewy morning), and then it twists in the opposite direction as it dries out (in the heat of the day). This twisting and untwisting forces the seed into the ground. The tip of each seed has tiny “one-way” barbs that allow the seed to drill into the soil but help keep it from pulling back out of the ground.

The trouble is, these seeds can also catch in a sheep’s wool and screw into its flesh. Porcupine grass can kill sheep that are allowed to graze on a prairie when the grass has gone to seed.

This article was prepared for the Natural Land Institute by John White, Ecological Services, 904 S. Anderson St., Urbana, Ill., Edition of June 9, 2005.

From the Oct. 5-11, 2005, issue

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