Forest Preserve District of Cook County, Illinois
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Grass Fires
Nature Bulletin No. 377-A   April 11, 1970
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Grass Fires
Illinois is the Prairie State. Perhaps we should not mention it here but the curious fact is that some of our original midwestern prairies were actually preserved as such by fire -- fires started every spring by the Indians to drive out the game hidden in that tall thick growth; fires to deprive their enemies of cover through which they might creep unobserved. Trees and shrubs grew along the streams, on wooded knolls or ridges, and in occasional "oak openings", but any woody seedlings that managed to get started in the adjacent prairie were killed by fire. The prairie plants survived because the sod was so thick and they were largely perennials with deep root systems or had other protective habits of growth.

In the Chicago region, in autumn and early spring, it was customary for people to burn off vacant lots in built-up areas and set fire to the grasslands in outlying subdivisions where there were but a few scattered homes. When it was windy and the vegetation thick and tall, these became leaping crackling flames that raced faster than a man can run. Some fires spread into nearby forest preserves and did irreparable damage Thousands of acres were left black and bare.

It was a foolish dangerous custom. It originated from the mistaken notion that fire destroys the weeds and gives desirable grasses a better chance to grow. In outlying subdivisions, isolated home owners burned to "improve" the pasture for their cows, goats or other livestock and, also, to protect their homes against fires started accidentally or by mischievous youngsters when the men were away at work.

It is far better to mow such vacant lots and meadows in early fall, and rake or plow a narrow firebreak around adjacent buildings. The mowed vegetation protects the soil and, as it decays, adds humus and fertility. Burning robs the topsoil of its fertility, kills the valuable forage plants such as bluegrass, clover and timothy, and actually increases the growth of quackgrass, weeds, and other unwanted, troublesome, perennial plants -- most of them introduced from foreign lands. Many of these have hardy seeds so well protected that they are not destroyed by fire; or vigorous rootstocks that remain undamaged.

There was a time when burning was also advocated as means of controlling insect pests. It is now known that burning encourages them by destroying beneficial insects, such as those that prey on other insects, and by destroying the necessary cover and food for ground- nesting birds such as the meadow lark, horned lark, bobolink, the native sparrows, killdeer, spotted sandpiper, quail, pheasant and marsh hawk. Some of these, and their young, feed largely on insects.

Grasshoppers, and other insects pass through the winter as eggs within the soil where fire cannot reach them. Others hibernate there as pupae. White grubs and wireworms burrow below the frost line. Many insect pests harmful to crops -- such as the army worm, chinch bug, corn borer and others -- burrow deep into large plant stalks which frequently are not consumed by a grass fire.

Fire, admittedly, was an ally of the native plants in our original prairies but only a few remnants of them remain. In their place we have many pesky worthless weeds and grasses from other countries Annual burning helps these spread and replace the valuable Plants we need. Fire is their friend.


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