LUCERNE — Guy Denny looked up into the sky, then bent over and picked up a leaf, letting it fall to the ground.
“I don’t like the way it’s changing,” Denny said. “This could be tricky.”
Although the day was warm, with light clouds, the light and variable winds were in the process of shifting from northeast to southeast; whichever way they ran would matter a great deal to Denny, who was preparing to set a large part of his property on fire.
After the test burn of a small brush strip, Denny and his helpers, including fire experts and EPA personnel, decided to tackle a sizable hillside prairie. First they burned a “black line” on the side away from the wind, so that the main fire couldn’t gather too much momentum and carry over into a neighboring corn field. Then Denny walked around the fire, “wrapping” it, using his drip torch with its 50/50 mix of diesel fuel and gasoline to set aflame the edge of the field closest to the prevailing winds, on the opposite side of the black strip. The fire caught and suddenly surged forward into the tall grass, pushed by the wind. According to Denny, the rushing wall of flame is known as a “head fire.”
“You use the wind to your advantage,” Denny said.
The variable winds resulted in a few moments when the fire shifted, sending a thick cloud of smoke directly at the observers. Denny said that if the winds had been much higher than 5 mph he would have canceled the burn, as variable or shifting winds can be very dangerous when a large fire with plenty of fuel is involved. Such shifts are dreaded by wildfire fighters out West, because they can result in firefighters becoming trapped by the fire. Denny said that pioneer accounts of wildfires on the Darby Plains in Madison and Union counties tell of sudden wind shifts driving a six-mile-long head fire faster than a man on horseback could outrun.
At the peak of the hillside prairie burn Tuesday, the flames leaped 20 feet into the air and roared like a waterfall. A small rodent dashed out of the brush and ran for safety as the fire flashed across the four-acre field in mere moments, releasing incredible heat. The prairie burn was a controlled emulation of what would often happen naturally in the past, sparked by lightning in spring thunderstorms, clearing last year’s growth and fertilizing the ground for new growth.
For thousands of years, tall grass prairie covered much of interior North America, from the Great Plains all the way east to Ohio. The eastern fringes of big prairie country made it as far as western Knox County, but these areas were mostly lost to pioneer farming and later to development. A few original areas remain in places like Killdeer Plains in Marion and Wyandot counties, and the prairie remnant strips surrounding the railroad near Claridon, just outside of Marion, but in recent decades, efforts have been made to restore prairie habitats throughout the state.
Denny began planting tall grass prairie around his home, just past Lucerne in western Knox County, near the Morrow County line, about 14 years ago. Over the years, he has gradually expanded the area to cover 20 acres. The land is dotted with bird houses, especially bluebird boxes. A pond on the property is active with toads, and many small animals make use of the prairie habitat.
Denny was joined for the burn on Tuesday by several helpers and by numerous observers, including officials from the Ohio Environmental Council.
Helper George Ellis said it was important to understand that the burn doesn’t destroy the prairie, it only renews it.
“A prairie’s like an iceberg,” Ellis said. “Two-thirds of it is below ground, where you can’t see it.”
Ellis said the burn removes the top growth, turning it into ash that can be reabsorbed into the soil as nutrients. The bottom growth of the plant remains undisturbed, and will grow again after the fire.
Even though the burn releases a tremendous amount of heat, the heat travels up and out. Denny said temperature readings taken underground during burns have shown that the fire passes overhead so quickly, the temperatures don’t rise very much underground. Thus the burn effectively prunes the plant and fertilizes it for a year of new growth.
“That’s pretty daunting,” said Jim Stickle of Mount Vernon as he looked at the rushing, roaring fire. Stickle and his wife, Marguerite, had come to observe the burn in hopes of learning how to do a controlled burn of his own prairie land. He found the size and speed of the fire a concern, particularly if he were to attempt a burn by himself, as Denny often does, but said it was certainly a much more efficient approach than mowing.
“Maybe I’ll start small,” Stickle said.
Jeff St. Clair of the Ohio Environmental Council said this was the first occasion he’d had to see the burn at Denny’s prairie, which has been featured numerous times on tours sponsored by the OEC.
“This place is just gorgeous once it grows up in midsummer,” St. Clair said.
