Cogon grass can be tough to kill. Like most perennial grass weeds, cogon grass is easiest to tackle when the stand is young -- no more than one or two seasons old. Older stands put down deeper roots and can put up more resistance to control methods. Physical and chemical control methods will kill most young stands of cogon grass in a single growing season. Older stands must be retreated for three seasons or more to be completely eradicated.
Things You'll Need
- Hand tiller, shovel or garden rake
- Glyphosate herbicide
Till the soil in the spring to a depth of 6 inches. A hand tiller, garden rake or shovel will get the job done. Mix and turn the soil so that the bottom layer is near the top and vice versa. Clean any clinging roots off of your tilling tool after each use. If these roots get deposited in other areas of your yard, they will sprout new cogon grass plants. Re-till the soil every six to eight weeks for the rest of the growing season. Do not water the soil during this time.
Mow the cogon grass at the lowest height possible on your lawn mower. Keep the grass at this height with repeated mowing throughout the growing season. Keeping the blades short will starve the cogon grass' underground rhizomes, stunt its growth and eventually kill it over several seasons. For more effective control, apply herbicide to any regrowth the following season.
Spray the cogon grass with a glyphosate herbicide in early fall. Follow the manufacturer's instructions and coat the entire surface of the grass blades. Re-spray the cogon grass each subsequent spring and fall until there is no more regrowth.