Controlling Johnson Grass – How To Kill Johnson Grass

Image by Don O'Brien

By Becca Badgett
(Co-author of How to Grow an EMERGENCY Garden)

Johnson grass (Sorghum halepense) has plagued farmers since its introduction as a forage crop. This invasive and noxious weed has gotten so out of control that many states require landowners to kill Johnson grass. If you are a landowner bothered by a troublesome invasion of the perennial weed, you probably just want to get rid of Johnson grass.

How to Get Rid of Johnson Grass

As with most invasive weeds and grasses, using multiple strategies usually works best for Johnson grass control. This means that you may use a Johnson grass herbicide program along with other kinds of Johnson grass control methods. This is fitting, as Johnson grass reproduces and invades crop areas in two ways, spreading both by seed and rhizomes to overtake farmland and other areas of your property. The rhizomes of Johnson grass are identified by thick cream-colored rhizomes, covered with orange scales.

Herbicides alone are usually not enough to be an effective Johnson grass killer. When combined with cultural practices that prevent the spread of rhizomes and seeds, a Johnson grass herbicide program, with repeated applications, may provide enough Johnson grass control to eliminate it.

Tilling the soil in fall following the harvest and followed with an herbicide is a good start to kill Johnson grass. Rhizomes and seed heads brought to the surface by tilling may be destroyed in this manner.

The seeds of Johnson grass that are missed during the applications can remain viable for as long as 10 years so it is best to prevent the seeds from being spread in the first place. Take steps to prevent the spread of seeds and rhizomes to areas that are not infested. Digging clumps of Johnson grass in the yard or small garden is a start. Dispose of the clumps where they cannot reseed or spread. It is best to do this before the grass goes to seed, to further prevent the spread of the seeds.

When Johnson grass grows near the lawn, keep the turf thick and healthy to discourage the invasion of Johnson grass. Take a soil test and apply recommended amendments to keep the grass growing. Reseed thin areas of the lawn and mow at the proper height for your variety of grass to keep it healthy and competitive against the Johnson grass.

Recommended Johnson Grass Herbicides

Successful Johnson grass control may include the use of Johnson grass herbicide. Post emergence products as “fluazifop (Fusilade II), sethoxydim (Vantage), clethodim (Envoy), and imazapic (Plateau)” may be effective in outlying areas of the property. Glyphosate (Roundup) may work as Johnson grass control near the lawn, but can damage surrounding turf.

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