by Invasive Species Coordinator Katie Biggert and Public Information Coordinator Madeline Stewart
Cogongrass (Imperata cylindrica) is one of the most invasive plants on the planet. Found on every continent except Antarctica, cogongrass is even a pest in its native Southeast Asia.
It is particularly insidious as a pest of our forests; it can tolerate the low light conditions in healthy forests, exploding when more light is let in. Cogongrass increases fuel loads, so forest fires or prescribed burns in infested stands can get hotter than the trees can stand. When the trees die, the increased light allows the cogongrass to explode, effectively converting a forest to grassland.
And no, livestock won’t forage on it because it is too tough and has low protein content.
Identification
Usually light green in color, this species has an offset midrib and flops over onto itself or other plants. Pencil-sized (and pointy!) rhizomes are found below the soil surface, and feathery flowers can be seen in spring.
Spread
Rhizomes that get stuck on bulldozers or other equipment, making it a good practice to rinse your equipment after visiting a site that potentially has cogongrass. Soil disturbance and movement is a main way of spreading cogongrass.
Management
Tilling up cogongrass can worsen infestations by dividing rhizomes. Herbicides, particularly imazapyr and glyphosate, applied according to the label’s instructions, are very effective if applied strategically and repeatedly. Herbicides can be applied after burning an infestation once the rhizomes sprout again.
Applications in the fall are more effective, as the grass is mobilizing its sugars to the rhizome for the winter and will take the herbicide with it.
Contact
If you think you know of a cogongrass infestation, contact the Clemson Invasive Species Program.