Search
Cogongrass, Imperata cylindrica (L.) Beauv., is a perennial C4 rhizomatous grass ranked among the world’s 100 worst invasive species due to its strong negative impacts on native plant communities (MacDonald, 2004; Estrada & Flory, 2015). It spreads aggressively through underground rhizomes and wind-dispersed seeds, forming dense monocultures that suppress native vegetation, alter fire regimes, and threaten agricultural and forestry systems (Bryson & Carter, 1993). Cogongrass thrives across diverse soils—from clay to sand—and under a wide range of nutrient conditions (Bryson et al., 2010).
Cogongrass is a globally recognized weed, reported as a pest in over 70 countries and widely established in the southeastern United States. It was accidentally introduced to Alabama in the early 1900s and later intentionally planted in Florida and other states for forage and erosion control—before its invasive nature was fully understood. Today, cogongrass has spread throughout nearly all Florida counties, often dominating entire pastures (Sellers et al., 2012). In Louisiana, it has been present since 1990, when initial surveys and an eradication plan were launched. Its distribution remains largely concentrated in the eastern part of the state.
Cogongrass observations in Louisiana
Cogongrass typically forms circular infestations, and is characterized by yellow-green, serrated leaves that grow 2–6 feet tall and feature a distinctive off-center white midrib. In spring or following disturbance, it produces fluffy white seed heads measuring 2–8 inches long, each capable of releasing up to 3,000 wind-dispersed seeds. Belowground, its white, highly branched rhizomes have sharp, pointed tips that can pierce the roots of other plants, facilitating its spread (Sellers et al., 2012).
Cogongrass leaf
Cogongrass with seeds. Picture by R. Díaz
Cogongrass reproduces by both rhizomes and seeds. Rhizomes are the primary mode of spread, enabling rapid regrowth after fire, mowing, or herbicide application. Seed dispersal, though variable in viability, aids long-distance colonization and is facilitated by wind and human activities such as soil movement and contaminated equipment (Bryson & Carter, 1993).
Rhizomes
Cogongrass with seeds. Picture by R. Díaz.
Cogongrass outcompetes native plants for resources, reduces biodiversity, alters soil nutrient dynamics, and increases fire intensity and frequency. This plant creates dense mats that prevent the establishment of native seedlings, thereby reshaping natural plant communities (MacDonald, 2004). Cogongrass in Louisiana was first discovered in 1990 in Washington Parish and has since spread to most of the southeastern parishes and some western and central parishes, and it’s causing a big impact in local areas due to the difficulty controlling its growth.
In forestry systems, cogongrass suppresses pine seedling growth and survival, complicates reforestation, and increases management costs (Daneshgar et al., 2008). Its presence exacerbates wildfire hazards: cogongrass-fueled fires burn hotter and spread faster than those fueled by native understory vegetation, causing extensive tree mortality. After such fires, cogongrass often re-sprouts quickly, reinforcing its dominance while native vegetation struggles to recover (Dozier et al., 1998).
Cogongrass
infestation in Baton Rouge, Louisiana
Effective cogongrass control requires long-term, integrated management, as no single method ensures eradication. Mechanical approaches such as mowing and tillage can reduce aboveground growth but often leave rhizomes intact or fragmented, leading to rapid regrowth unless combined with chemical treatments; mulching or solarization may help in small infestations but are impractical at large scales. Chemical control with glyphosate and imazapyr remains the most effective strategy, especially when applied in late summer to early fall, though multiple applications over several years are typically needed to achieve substantial population reduction (Bryson & Carter, 1993; Dozier et al., 1998; MacDonald, 2004).
Biological control efforts are ongoing but remain in the exploratory stage. Potential agents, including insects and fungal pathogens from cogongrass’s native range (e.g. shoot tip borer Atherigona sp., and the crown borer Emmalocera latilimbella.), are being studied. To date, no biocontrol organisms have been released in the U.S. due to concerns about non-target effects and insufficient host specificity (Agricultural Research Service, 2024).
Bryson, C. T., & Carter, R. (1993). Cogongrass, Imperata cylindrica, in the United States. Weed Technology, 7(4), 1005–1009.
Bryson, C. T., Krutz, L. J., Ervin, G. N., Reddy, K. N., & Jr, J. D. B. (2010). Ecotype Variability and Edaphic Characteristics for Cogongrass (Imperata cylindrica) Populations in Mississippi. Invasive Plant Science and Management, 3(3), 199–207. https://doi.org/10.1614/IPSM-D-09-00029.1
Daneshgar, P., Jose, S., Collins, A., & Ramsey, C. (2008). Cogongrass (Imperata cylindrica), an Alien Invasive Grass, Reduces Survival and Productivity of an Establishing Pine Forest. Forest Science, 54(6), 579–587. https://doi.org/10.1093/forestscience/54.6.579
Dozier, H., Gaffney, J. F., McDonald, S. K., Johnson, E. R. R. L., & Shilling, D. G. (1998). Cogongrass in the United States: History, Ecology, Impacts, and Management. Weed Technology, 12(4), 737–743.
Estrada, J. A., & Flory, S. L. (2015). Cogongrass (Imperata cylindrica) invasions in the US: Mechanisms, impacts, and threats to biodiversity. Global Ecology and Conservation, 3, 1–10. https://doi.org/10.1016/j.gecco.2014.10.014
MacDonald, G. E. (2004). Cogongrass (Imperata cylindrica)—Biology, Ecology, and Management. Critical Reviews in Plant Sciences, 23(5), 367–380. https://doi.org/10.1080/07352680490505114
Sellers, B. A., Ferrell, J. A., MacDonald, G. E., Langeland, K. A., & Flory, S. L. (2012). Cogongrass (Imperata cylindrica) Biology, Ecology, and Management in Florida Grazing Lands: SS-AGR-52/WG202, rev. 8/2012. EDIS, 2012(8). https://doi.org/10.32473/edis-wg202-2012
Agricultural Research Service (2024). Can Biocontrol Halt the Spread of Invasive Cogongrass? Can Biocontrol Halt the Spread of Invasive Cogongrass? : USDA ARS
Authors: Nahomi Lopez, Rodrigo Diaz
