Prescribed burn frequently asked questions.
Q. Why do I see burned patches in the woods and prairies at The Morton Arboretum?
A. Those are the evidence of prescribed burns (also called controlled burns), an essential practice for restoring and maintaining healthy natural areas at the Arboretum. In a prescribed burn, trained stewards use safe techniques to burn dead stalks and undergrowth. This practice is essential to the health of our native plants and the birds and other wildlife that depend on them. Without this controlled use of fire, the Arboretum would be far less beautiful and would not provide such good habitat. Forests managed with controlled burns are not only healthier but safer: Without them, dry, dead undergrowth builds up and eventually can provide fuel for dangerous forest fires.
Q. Why is fire important?
A. Fire is a normal part of the life cycle of natural ecosystems in most areas of the United States. Before the Midwest was settled in the 1820s and 1830s, fires, set by mainly by American Indians, burned the prairies every one to four years. Woodlands burned at longer intervals. When settlers came, they suppressed the fires, allowing invasive plants and other woody vegetation to grow thick in natural areas. In the last half-century, scientists who study ecology have come to understand how crucial fire is to these plants and ecosystems, both prairies and oak-dominated woodlands. Now we know that you can’t have healthy natural areas without fire.
Q. How do you conduct these burns?
A. We burn small areas at a time in a very controlled way. The staff and stewards who conduct the burns are highly trained and use special safety equipment. Each burn is carefully planned. A technician uses a special torch to burn away the undergrowth in a small area, while others help extinguishes the fire as soon as it is safe and has done its work. The flames stay low and contained. Ideally, the fires go out by themselves, but technicians are always nearby to douse them if needed.
Q. How do you plan burns?
A. We make every effort to minimize the impact of burns. We burn only when the weather is appropriate, with no high winds to spread the fire or blow smoke off our property. For safety, visitors are sometimes excluded from the area of controlled burns. Every controlled burn at the Arboretum has the required permits.
Q. What determines when you burn?
A. We can only do prescribed burns when there is dead, dried plant material to burn and it is not wet from rain or snow. Most burns are undertaken in early spring, when dead stalks and leaves are still on the ground but spring rains have not yet started. Some burns are done in autumn, after trees’ leaves have fallen but before it snows. A burn is only done on a day with little wind when no rain or snow is forecast.
Q. Is this a new thing?
A. The Arboretum has been conducting controlled burns in our prairie since the 1960s and throughout our other natural areas, including woodlands, since the 1980s.
Q. How does the fire help the plants?
A. The fire helps control many weedy and invasive plants that would compete with the native plants. In spring, the black soil that is left after a burn absorbs sunlight and warms up quickly, so seeds can germinate and native plants can start growing. The ash from the burned plants recycles nutrients back to the soil.
Q. Will the burned areas stay black?
A. Within two to three weeks in spring, prairie plants will sprout and grow back taller, more vigorous, and often with more flowers. When a prescribed burn is done on the forest floor, wildflowers are usually more abundant the next spring. If you look closely, you may see evidence of fire, such as lightly charred fallen logs, but in general, burns make the woods and the prairie more green and beautiful.
Q. How can the plants sprout if you burned them?
A. The fire consumes only the dried-out top growth, which has already died. The roots and growing points of the plants are still alive, safe underground, ready to sprout once the ground is cleared by the fire. Since these native plants evolved with fire, they are well adapted to regular burning. Some plants’ seeds even need fire to sprout.
Q. Doesn’t the fire in the woods hurt the trees?
A. Oak trees, which dominate our woodlands, have thick, fire-resistant bark and tolerate fires as a normal part of their life cycle. Controlled burns in the woods do burn away many small tree seedlings, but this helps keep the woodlands open and filled with sunlight, which helps other saplings grow. Burning conserves the forest ecosystem overall.
Q. Does this pollute the air?
A. The Environmental Protection Agency has found that smoke from prescribed burns has no significant effect on air quality.
Q. Is this just an Arboretum practice?
A. Prescribed burning is a fundamental and widespread practice for managing natural areas. Burns are conducted in many state and national parks, forest preserves, national forests, and other natural areas.