In 1921, America introduced cogongrass as a forage crop; later used for soil control, the invasive grass now covers more than 1 million acres in Florida

Cogongrass seems to have been an appealing solution for a common agricultural concern in the early 1920s. The fast-growing grass, native to Southeast Asia, was introduced to Mississippi from Japan in 1921 as a potential forage crop for cattle. A decade later, the plant was used for a different role when it was introduced by agencies in different regions of the South in an attempt to stabilize eroding soils. A good conservation method became one of the most harmful invasive plant species in the U.S.

The plant is found today on more than 1 million acres of land in the state of Florida, and the problem is present in the whole Southeastern region as well. The USDA Animal and Plant Health Inspection Service's Cogongrass Control Program Environmental Assessment, this plant manages to spread its seeds and rhizomes thanks to its rapid growth, thus overpowering other native plants and reducing forest productivity.

The grass that arrived as a solution


Cogongrass (Imperata cylindrica) came to America in two distinct time frames. The first time was in 1912, when it was brought to Mobile, Alabama, as packing material for the shipment of citrus rootstocks from Japan. The second time was in 1921, when it was imported to Mississippi for use as a forage crop for livestock. It was a rational idea because cogongrass is known to be fast-growing as well as drought-resistant, but it failed to work in practice.

During the 1930s and 1940s, plants from the Mississippi trials were distributed in Florida and other Southern states for erosion control, mine reclamation, and soil stabilization. The USDA Forest Service research review on cogongrass documents the plant’s early introduction, later use in erosion control, and its spread across the southeastern United States. Thousands of acres were planted across the region during conservation efforts aimed at erosion control. Unfortunately, cattle did not prefer cogongrass and refused to graze on it. Over time, cogongrass leaves became sharp and dangerous due to silica accumulation.

When the perfect plant became the problem

The very characteristics that made cogongrass attractive to land managers allowed it to escape cultivation. Unlike many grasses, cogongrass spreads in two ways. It scatters through the wind by means of white fluffy seeds, and it develops new shoots through below-ground rhizomes. Even small fragments of those rhizomes can establish entirely new infestations after mowing, construction, or soil movement.

Over the years, it has managed to spread far beyond the place of its original cultivation and has colonized new environments from roadsides to forests, utility strips, pastures, orchards, and public lands everywhere. Moreover, instead of blending into existing ecosystems, cogongrass formed dense monocultures that crowded out native plants before they had a chance to grow.

Why it is so difficult to remove

Most invasive plants thrive because they produce many abundant seeds. In addition to this, cogongrass also keeps a large amount of energy underground. Cogongrass stores significant energy in its underground rhizomes, allowing it to regenerate quickly after being cut, burned, or mowed. Fire can benefit cogongrass because its underground stems remain intact while surrounding native vegetation is damaged. Also, the density of cogongrass creates fires that are very hot and affect the ecosystem. Therefore, land managers often require repeated herbicide applications and long-term monitoring to prevent regrowth.

An expensive lesson in unintended consequences

Cogongrass has been classified as a federal noxious weed and is regarded as one of the most troublesome invasive plants globally. The weed has been found in several areas across 12 states in the U.S. However, the largest infestations of the plant remain in the southeastern part of the country. The plant not only disrupts forests, but it also poses a danger to wildlife areas, pastures, highways, and regeneration operations, while hundreds of millions of dollars are lost annually in its management.

The history of cogongrass reflects a broader pattern in which introduced species can create unintended ecological problems. Initially, it was brought to the United States to feed livestock and stabilize soils, but the same traits that made it useful also contributed to its spread as an invasive species. The very same traits, however, made it impossible to contain once it escaped cultivation.

The lesson hidden beneath the grass

Cogongrass has never been brought to America to hurt the landscapes of this nation. This grass was adopted because it was able to grow in areas where other plants could not grow, it withstood hard conditions, and it looked like a solution to environmental problems. However, ecosystems seldom behave the way people want them to behave.

It is more than one hundred years since cogongrass has come to America, and it keeps on spreading in the southern regions of the country. The case illustrates how traits that make a species useful in one setting can also contribute to ecological problems when it spreads beyond its intended environment.