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Johnsongrass (Sorghum halepense) is an aggressive perennial that is common in agronomic fields, along roadways and waterways, and in low lying areas that are prone to flooding. Mature leaf blades are 5 to 20 inches long with obvious white ribs down the centers. Plants reproduce by seed and by perennial rhizomes, making control difficult. Rhizomes are stout compared to other grasses and can develop in as little as one month from seed germination. 

Johnsongrass growth habit.

(Photo: Chris Evans, University of Illinois, Bugwood.org)

Johnsongrass flower heads.

(Photo: Ohio State Weed Laboratory, The Ohio State University, Bugwood.org)

Management:

• Apply pre-emergent herbicides to help prevent or reduce seedling establishment.
• Post-emergent herbicides selective for grasses can be applied when plants are seedlings, but these are less effective once rhizomes have formed.
• Avoid cultivation, which spreads plants.

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