Cogongrass

A federal noxious weed and one of the world's worst invasive grasses - cogongrass forms dense mats that exclude everything else and burns dangerously hot. Never plant it; this entry is for identifying, reporting, and controlling it.

How to recognize it and why never to plant it: a clumpless, spreading grass with an off-center whitish midrib and sharp blades that forms dense rhizome mats excluding all other vegetation.

You must never plant cogongrass - and as a federal noxious weed it's illegal to - so recognizing it is what matters. It grows as dense, often circular and outward-spreading patches of yellow-green to tan grass, 1-4 feet tall, with a few tell-tale features: each leaf blade has a distinctly off-center whitish midrib (not down the center), the blade edges are minutely serrated and sharp (rough to the touch, hence 'speargrass'), and the patch has no clear individual clumps - it's a solid mat rather than discrete bunches.

Below ground is its engine: a dense network of hard, sharp, whitish rhizomes just under the surface, which can make up most of the plant's mass and store the energy that makes it so hard to kill. In spring it produces fluffy silvery-white plumes that shed clouds of wind-borne seed. It thrives in poor, disturbed, sandy soils in sun to part shade and tolerates a very wide range of conditions. Understanding how it spreads - both far, by seed, and relentlessly outward, by rhizome - and how it excludes everything else and fuels hot fires is exactly why it belongs firmly in the 'never plant, report and control' category.

How it spreads - two engines at once: fluffy wind-borne seed carries it to distant new sites, while a dense mat of sharp rhizomes expands each patch and regrows from any surviving fragment.

Cogongrass spreads by two independent means, which is why it's so hard to contain. Its spring plumes release huge numbers of tiny, cottony, wind-borne seeds that can travel long distances, founding brand-new infestations far from any existing patch - so outlier patches can appear seemingly out of nowhere, downwind of a source.

Locally, it advances by an aggressive network of rhizomes - hard, sharp, segmented underground stems that push outward to expand the mat and store reserves. It regrows readily from rhizome fragments, so any activity that chops and moves the soil - tilling, grading, mowing decks, contaminated fill, dirty equipment - can carry pieces to new ground and start fresh patches. Fire and mowing, rather than killing it, tend to stimulate rhizome resprouting and flowering. This combination of long-distance seed dispersal and tenacious, fragment-spread rhizomes means control must target the rhizomes over multiple years and must scrupulously avoid moving infested soil or equipment.

Control, not care: report it, then attack the rhizomes over multiple years with repeated tillage and/or systemic herbicide; never just mow or burn (that rewards it), and never move infested soil or equipment.

For cogongrass, 'care' means reporting and controlling - and because it's a federal noxious weed, new infestations should be reported to your state agriculture department or extension office, which can advise on treatment and, in some cases, help. Control is a genuine multi-year campaign targeting the rhizomes: the effective tools are repeated deep tillage that dries out and exhausts rhizomes (in suitable settings) and/or systemic herbicide applied to actively growing foliage over several seasons, often in combination. There is no quick fix.

Crucially, avoid the things that reward it: mowing and burning alone don't kill it - they stimulate resprouting and flowering - and any soil disturbance that isn't part of a control plan can spread rhizome fragments. Never move infested soil, fill, or equipment without cleaning, and prioritize isolated outlier patches to stop long-distance spread. Wear gloves and eye protection against the sharp blades, and treat cured infestations near buildings as a fire hazard. Once a patch is cleared, replant and maintain desirable cover - native warm-season grasses such as little bluestem, muhly, or wiregrass - so bare ground doesn't invite reinvasion. For anything beyond a tiny new patch, work with professionals and local invasive-species programs.

Not a food and not useful forage - livestock avoid its sharp, low-quality blades. Ecologically its impact is starkly negative: it excludes native plants and fuels destructive fires, degrading whole habitats.

Cogongrass is not a human food, and it's poor even as forage: its blades are tough, sharp, and low in nutrition, so livestock avoid it and it offers little grazing value. (Its rhizomes have some traditional medicinal use in Asia, but that's no reason whatsoever to tolerate the plant.)

Ecologically, its impact is overwhelmingly negative. Where cogongrass takes over, it forms near-total monocultures that exclude native grasses, wildflowers, and tree seedlings, stripping habitat and food from the wildlife that depends on diverse native plant communities. Then it makes things worse by changing the fire regime: its dense cured foliage burns so hot that it kills trees and native plants that would survive a normal fire, while its own rhizomes resprout - a feedback loop that lets it expand at the expense of the ecosystem. There's essentially no ecological upside to keeping it. The meaningful 'nutrition' story is what it destroys: removing cogongrass and restoring native cover brings back both the plant diversity and the safer, more natural fire behavior it eliminates.

Introduced to the US in the early 1900s - accidentally as packing material and deliberately as forage and erosion control - cogongrass escaped along the Gulf Coast to become a federal noxious weed.

Cogongrass reached the United States in the early 20th century by two routes. It arrived accidentally around 1912 as packing material in shipping crates at a Gulf Coast port, and it was later deliberately introduced and tested as a potential forage grass and for erosion control in the South. Both were mistakes: the plant found the warm, humid, sandy Southeast ideally suited, proved worthless as forage, and escaped to spread aggressively across the Gulf Coast and beyond.

Recognized as a serious menace, it was designated a federal noxious weed, making it illegal to sell, move, or plant across state lines, and it's the target of large-scale management efforts across the South. Complicating the picture, an ornamental red-leaved form - 'Japanese bloodgrass' (Imperata cylindrica 'Rubra') - has been sold as a garden grass, but it can revert to the aggressive green invasive form and is banned in some states, which is why it too should never be planted. Cogongrass is a stark example of how introducing a vigorous grass - even with good intentions like erosion control - can backfire catastrophically outside its native range.

Confirm it (clumpless spreading mat, off-center sharp-edged leaf midrib, silvery plumes, sharp white rhizomes), report it, attack the rhizomes over years, never move infested soil, and treat cured stands as fire fuel.

Is this cogongrass? Look for a dense, circular or spreading, clumpless grass patch that excludes other plants; leaf blades with an off-center whitish midrib and minutely serrated, sharp edges; fluffy silvery-white plumes in spring; and a dense mat of hard, sharp white rhizomes just under the soil. What should I do if I find it? Report it to your state agriculture department or extension office (it's a federal noxious weed) and get a control plan. How do I get rid of it? Multi-year control targeting the rhizomes - repeated tillage and/or systemic herbicide on growing foliage; there's no one-shot fix. Can I just mow or burn it? No - mowing and burning alone stimulate resprouting and flowering; burning also creates a serious fire hazard while the rhizomes survive. Why does it keep spreading? Wind-blown seed founds distant patches and rhizome fragments spread with moved soil and equipment - so never move infested soil or dirty equipment. Is 'Japanese bloodgrass' safe to plant? No - the ornamental red form can revert to the invasive green plant and is banned in some states. What should I plant instead? Native warm-season grasses such as little bluestem, muhly grass, or wiregrass.

Worst in the warm, humid Southeast and Gulf Coast (roughly zones 8-10), thriving in poor sandy disturbed soils; cold winters limit it farther north, but it is spreading and warming climate expands its range.

Cogongrass is most devastating in the warm, humid Southeast and along the Gulf Coast (roughly zones 8-10), where long growing seasons, mild winters, and abundant poor, sandy, disturbed soils - roadsides, cutover forest, pastures, mined and graded land - suit it perfectly. It's a sun-loving pioneer of open, disturbed ground, though it tolerates part shade and a wide range of conditions.

Colder winters limit its spread farther north, so its heartland is the Deep South; but it has expanded steadily, and a warming climate is expected to enlarge its potential range over time. Because it spreads by both long-distance wind-blown seed and rhizome fragments carried on soil and equipment, no warm-region landowner should assume they're safe. Wherever you are in or near its range, the guidance holds: never plant it (including the ornamental 'bloodgrass' form), learn to recognize its clumpless mats and off-center leaf midrib, report new infestations, and act early - a small outlier patch is enormously easier and cheaper to control than an established, seeding, fire-prone stand.