Guide to Johnsongrass Identification & Control

johnson grass

Type of Weed: Grassy Weed

Sorghum halepense


Johnsongrass is warm season perennial grassy weed. 

This fast-growing weed is commonly found across most of the southern United States, including Texas.

This vigorous weed typically grows in pastures, hay fields, along roadsides, and in undisturbed areas.

Johnsongrass’s underground rhizomes and seeds make it a difficult weed to control.

How to Identify

Johnsongrass has thick fibrous roots and rhizomes (which allow it to spread underground). Its vertical green stems are a flattened round shape and relatively smooth.

Its sheaths can be green to maroon, particularly near the base. Its bright green leaves are long, about 6 to 20 inches, with a distinct white midvein, and come to a blade tip at the end.

They do not have auricles, are rolled in the shoot, and are generally smooth on both sides. Its ligules are 3 to 4 millimeters long, contain fine hairs, and toothed towards the top.

It has flowers that are large, open panicles that have a purple tint to them. Seeds are oval and will be dark red to black once mature. If left un-mowed, Johnsongrass can reach heights of 6 ½ to 10 feet tall.

Control Methods

Control Difficulty: Moderate to Difficult

The easiest way to control this weed from spreading is through cultural control. Routine mowing will prevent it from flowering and setting seed. Mechanical control of digging will be the best way to remove and destroy Johnsongrass.

Dig deep and wide enough to remove all the rhizomes, this prevents it from spreading to new areas. This may not be feasible for some lots of land; therefore, chemical control is your next step. Using a selective post emergent grass herbicide during the growing season will deter further growth.

Applications may need to be done a couple times during the season. If you continue to struggle with Johnsongrass, you can use a non-selective herbicide. This not only kills the weed but it will also kill any surrounding grass or plants.

Be sure to reseed your lawn promptly or apply new sod in the bare spots, so they don’t become susceptible for more weed growth. Applying a selective pre-emergent grass herbicide in the spring and fall will help prevent new weeds from growing.

Prevention Tips

Having a dense, healthy lawn is the best way to deter weeds from growing and staying in your yard. This can be achieved by mowing your lawn at your turf’s proper height, routine aeration and fertilization, along with proper irrigation.

Using a combination of selective pre and post emergent herbicides throughout the year is an added layer of defense to protect your turf from pesky weeds.

Our team of highly trained technicians are experts with grassy weeds and can help get your lawn back to its proper health.
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