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Figure 1. Cogongrass fires burn hot! Note the dense thatch in the foreground.

AUBURN UNIVERSITY, Ala. – Cogongrass is one of the most significant non-native invasive plants in Alabama. Not only does it invade a wide variety of habitats, but it also disrupts ecosystem function, particularly through fire regimes and fire intensity.

Thrives On Fire

“Cogongrass is a fire-adapted species that thrives on fire,” said Nancy Loewenstein, an Alabama Extension forestry, wildlife and natural resources specialist.

It burns easily and at extremely high temperatures in part because of its leaf characteristics but also because plants often have highly flammable thatch (dead leaf material) at the base of the plants. Plants re-sprout quickly after fires because fires rarely harm their extensive rhizome system. Late winter fires can also promote flowering.

Ultimately, fire will make the cogongrass grow thicker, and produce more flowers and seeds which contribute to spread.

How to Identify

“One way to stop it from spreading is by increasing education so people can identify and avoid it,” Loewenstein said.

Identify cogongrass by its 2 to 3 feet tall leaves. These leaves are greenish-yellow and have a serrated margin. They will range from erect to floppy and turn a distinctive reddish-tan color in the winter.

“You’ll often see descriptions indicating that it has an offset white midrib, which is the case some of the time but not always,” she said. Also, several look-a-like grasses have offset white midribs which can cause some confusion.

The rhizomes, or underground stems, are strongly segmented, creamy white and covered with paper-like scales. The spring flowers serve as a helpful feature for the identification of cogongrass.

“The flowers are 2 to 8 inches long, starting out tan to purple in color, becoming silvery white,” Loewenstein said. “The seeds are light and fluffy like dandelion seeds.”

North Alabama may see the flowers bloom in May or early June, while south Alabama may see the blooms in early spring.

The cogongrass field guide can provide additional information on identifying the plant.

Controlling Cogongrass

Preventing spread is the best first step for control. Cogongrass can easily hitchhike and spread on all kinds of equipment. Avoid infestations when possible and clean equipment after working in areas infested with cogongrass.

Fire alone cannot be used to contain this invasive plant. However, controlled fires can be used to remove the thatch which is then replaced by lush growth that can be effectively sprayed with a herbicide.

According to Loewenstein, two effective herbicides, glyphosate and imazapyr, can provide control but it can take years of repeated treatment for the cogongrass to subside.

Learn more about controlling the spread of cogongrass here.

More Information

Find more information about cogongrass and the threat of fires at the Alabama Extension website, www.aces.edu.

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