Like an Old Testament prophet, Ray Dickens, now a retired Auburn University agronomy professor, was warning Alabamians more than 30 years ago about the heavy toll a noxious invasive weed ultimately would exact on the state and the Southeastern United States.
Today, many people in Alabama — forestry professionals, cattle producers, hunters, nursery professionals, road maintenance crews and many landowners — are becoming painfully aware of just how right he was about this virulent weed, often described out of a sense of frustration as the weed from hell, but more commonly known as cogongrass.
For many foresters, the virulent effects of cogongrass becomes most painfully apparent when they attempt to introduce new plantings to previously harvested forestland where huge understories of cogongrass are present.
“That is a recipe for complete stand failure,” says Stephen Enloe, an Alabama Cooperative Extension System weed scientist and Auburn University assistant professor of agronomy and soils.
That’s because the seedlings must compete with the aggressive weed for vital soil nutrients and water. And even if the seedlings manage to get a toehold, there is still no guarantee they will reach maturity because of the increased incidence of wildfires associated with cogongrass.
“Cogongrass produces tremendous above ground biomass that dries down every winter,” Enloe says, adding that it’s also high in silica, which enables this rich biomass to persist for many months.
What results over time is the buildup of especially incendiary material. Indeed, the presence of this thick biomass virtually ensures that fires caused by lightning strikes, cigarette butts and other factors will burn extremely hot, leading to the death of many fire-tolerant pine species.
Thankfully for the state’s row-crop farmers, cogongrass has not been as big a headache, Enloe says. Repeated weed cultivation — a chore that most farmers routinely undertake in late spring and during the summer — effectively breaks up of the plants rhizome layer and, when combined with good crop production practices, provides excellent control.
“Cogongrass is there, but it hasn’t affected (row-crop) farmers directly in terms of undermining crop yields,” Enloe says.
But it’s a different case with native and natural habitats. Enloe and other experts have marveled at its ability to out-compete and eventually shut out native flora.
Cogongrass has been in Alabama and much of the South for almost the past century, and, for a while, experienced what Enloe describes as a considerable lag phase.
“It sat there for many years, expanding very slowly, but that’s common with invasive plants,” Enloe says.
“During that lag period, many factors often come together that allow it to overcome barriers for its successful reproduction and dispersal.
Enloe says Dickens saw all of this coming three decades ago.
“He warned about the impending doom that was coming, but, unfortunately, his message was unheeded,” he says.
What started as a trickle has escalated into a cascade. Mapping efforts detected evidence of the plant not only along the Gulf Coast, where it first gained a toehold, but also in central and even north Alabama.
“Furthermore, our neighbors to the east in Georgia and South Carolina and to the north in Tennessee have discovered they are no longer free of the weed,” Enloe says, adding that “the plant hasn’t found its geographic limits.”
Cogongrass was inadvertently introduced into the Mobile Bay area in 1912 as packing material for Satsuma oranges from Japan. But a Philippine variety was also introduced as a possible forage crop in 1921 — unsuccessfully, as it turned out, but the established stands were never removed.
The rapid spread of cogongrass is made possible by two reproductive strategies: It’s creeping underground rhizomes and also by its light, fluffy seeds, which are carried by wind drift. But humans and animals alike also have contributed to its spread. Field dirt moved from one location to another is a major factor behind the weed’s spread.
“Cogongrass rhizomes are very drought tolerant and can be moved a long, long distance,” Enloe says.
He says the two best ways to control cogongrass are arresting its seed production and killing its rhizomes, especially difficult tasks, particularly when forestlands are involved.
Prescribed burning, one of the oldest and most effective methods for controlling forestland undergrowth, isn’t feasible with cogongrass, precisely because evolution has equipped the weed with a unique ability to bounce back from the ravages of fire.
“You can burn mature cogongrass, and in a few weeks you’ll have a pure, new stand in its place,” Enloe says.
The Alabama Cooperative Extension System is one of several organizations comprising a statewide cogongrass task force. The Alabama Forestry Commission, working through the task force, is planning between four and six workshops this year with the aim of educating Alabamians about the spread and containment of this invasive weed.