Cogongrass: Wanted Dead Or Alive

Getting jobs accomplished is always made a bit easier by getting help from trusted partners. Such is the case with the Georgia Forestry Commission’s ongoing quest to eradicate the invasive weed known as cogongrass from our state’s landscape.

“Outdoor enthusiasts are going to be the first people to set their eyes on it,” said Georgia Forestry Commission Forest Health Specialist Lynne Womack. “We need all the readers of GON and anyone who spends time outside to keep a lookout for it, especially in spring, when it’s easier to spot.”

Cogongrass is sometimes referred to by the names japgrass, blady grass, kunai, paillotte and santintail. Under any moniker, the weed has earned a top ranking on the GFC’s “Dirty Dozen” list: The Top Twelve Most Invasive Plants in Georgia. The list is rounded out by these other invasives: non-native privet, Nepalese browntop, Chinaberry, non-native lespedeza, kudzu, Chinese tallowtree, non-native olive, Japanese climbing fern, English ivy, Wisteria, Mimosa and Callery “Bradford” Pear.

A field of cogongrass is pretty to look at, but dangerous to have on your property.

According to documents provided by the University of Georgia Bugwood Network, the introduction of cogongrass into the United States was initially accidental. It hitched a ride in packing material used for the shipment of orange plants from Japan to Grand Bay, Ala. in the winter of 1912. Subsequent introductions were made in Florida and Mississippi where it was used as cattle forage and in test trials for erosion control. Cogongrass has since spread throughout the southeastern states from Alabama west through Mississippi to Louisiana and east to South Carolina. Cogongrass has now been discovered across 1.25 million acres in the southeastern United States.

Cogongrass not only makes Georgia’s “Dirty Dozen” list, but the noxious weed is also considered one of the top-10 worst weeds in the world because it is tough, drought-resistant and a known bully. Cogongrass can destroy entire ecosystems by crowding out native species of both plants and animals. Cogongrass not only replaces native plants, on which wildlife feed, but it also has very high silica content that is unpalatable to native wildlife. It outcompetes native grasses and forbs that are important to many threatened species, such as the gopher tortoise. It negatively impacts rights-of-way, reduces forest productivity, encroaches in pastureland, hayland and even golf course greens. 

If that’s not enough bad marks, cogongrass is highly flammable and thrives in areas where fire is a regular occurrence. Fires through cogongrass burn hotter, faster and higher than native grass fires. These factors can kill seedling trees and native plants, with heat so intense it can stress mature pine stands and lead to disease and insect infestation. And of course, this all spells trouble for people and structures in its path. 

“We’ve been dealing with it for quite some time,” said Mike Grimsley, owner of Boundary Woods Plantation, located in Decatur County. “We manage a lot of longleaf timber and notice it when we’re doing thinning. Just like Bahia and Bermuda grass, and even Japanese climbing fern, there could be a small area of seed in a stand and it gets spread around when the loggers come in.”

Grimsley said as soon as he or his crew members spot cogongrass in its trademark circular growth pattern, they mark its perimeter with flagging tape. He wastes no time getting in touch with Georgia Forestry Commission Forest Health Specialist for southwest Georgia, Mark McClure. McClure visits the site within two weeks and calculates the infestation’s GPS coordinates. He then devises a spray schedule to begin the eradication process. 

“If you get on it pretty quick, you have a good chance of stopping it,” said Grimsley. “If you let it sit a couple of years, it can move into a much larger section of the forest.”

McClure said, “We’ve been monitoring sites with Mike for over 10 years. We’re constantly monitoring existing spots and locating new spots. The herbicide treatments have been very effective.”

Grimsley’s company is located in one of the most active cogongrass counties in the state, according to data gathered by the GFC. Decatur, Early, Seminole, Grady, Thomas and Carroll counties have the most cogongrass spots in Georgia. It often shows up in pine woodlands, along rights-of-way (both utility and vehicle), open areas such as pastures, wildlife food plots and home landscapes. Some unique detections have been made in pond dams, welcome centers, flower beds and dunes along the coastal shore. 

Time To Look For The Fluff

Cogongrass has some distinctive features that can help us identify it. It’s especially showy in spring. 

Between April and June, cogongrass goes into its flowering stage, producing fluffy, white, plume-like seed heads that would be considered pretty if they weren’t so dangerous. The wily weed can initiate flowering at other times of the year in response to a disturbance, such as mowing, fire, herbicide application or the first hard frost. Seed heads range in size from 2 to 8 inches in length and can contain as many as 3,000 seeds. These seeds bear silky, white hairs that blow off like dandelion seeds, making them easily scattered by the wind.

The circular growth pattern of cogongrass is another identifier, along with leaves measuring a half-inch to an inch wide. They commonly grow 12 to 30 inches long and have a yellowish-green appearance. The leaves have an off-center mid-rib and are rough to the touch with tiny serrated edges. Grazing animals don’t like it due to the silica content, which is high in the weed, making cogongrass a useless forage crop. In Georgia, patches of cogongrass typically measure between 0.10 and 0.25 acres.

Cogongrass rhizomes are also somewhat simple to identify. They’re white, segmented  and scaly, and they form a dense root mat 12 to 16 inches or more below the soil surface. They have sharp points, and each segment can give rise to a new plant.

Found Some! Now What?

“All new potential cogongrass detections should be reported to the local GFC office,” said McClure. “We’re continuing to treat new spots for landowners at no cost, with herbicide treatments beginning in May. The spots will be monitored and treated annually until eradicated.”

Close-up of a cogongrass seed head with silky white hairs that help it spread.

Last year marked the 15th year the GFC has had a lead role in the cogongrass detection and eradication program. In addition to on-site identification and eradication services, the GFC has sponsored workshops, presentations, field days and more.

“Educating the public about why cogongrass is so dangerous to ecosystems—and helping people learn how to identify it—has been extremely successful,” said McClure. 

“The success of any statewide program like this is dependent on federal, state and local government partnerships, along with private industry and landowners. Between us all, we are making a difference.”

That is evidenced by the record-high number of cogongrass detections made in 2021. With 156 new detections, the total number of cogongrass spots in Georgia comes to 1,621, scattered across 418 acres in 72 counties.

There are no generic recommendations for control of cogongrass, so treatments should be site-specific and considerate of surroundings. Of herbicides tested and used on the weed, the active ingredients “glyphosate” or “imazapyr” have shown positive results. Both, however, may cause injury to non-target plants.

Despite its aggressiveness, cogongrass is being defeated in Georgia through the efforts of several partners, and according to McClure, it’s challenging and worthwhile to convert infected areas back to native environments.

“It’s great to work with landowners whose woodlands have been impacted by cogongrass and then follow the eradication process to a successful close,” McClure said. “To see that site converted back to native vegetation is really very rewarding.”

Cogonograss grows in a circular pattern with a thick-thatched root base. Photo by Chuck Bargeron, University of Georgia, Bugwood.org