Johnsongrass Control in Turf

Johnsongrass is a tall perennial grass that spreads by seed and thick scaly rhizomes. It is more common around turf edges, roadsides, and disturbed sites than in dense closely mown turf.

How to Identify Johnsongrass

Broad leaves have a prominent pale midrib, and open purple-tinged seedheads rise well above turf. White rhizomes are thick, segmented, and sharply pointed.

Why It Appears in Turf

Disturbance, imported soil, neglected borders, and movement of rhizomes allow patches to expand. Mowing suppresses seedheads but does not remove underground reserves.

Make the Site Less Favorable

• Maintain the recommended mowing height and avoid scalping.
• Correct irrigation, drainage, compaction, fertility, or shade problems that thin desirable turf.
• Repair bare areas and use adapted turf cultivars to close openings where seedlings establish.

What University Research and Extension Guidance Says

University guidance shows that systemic products capable of reaching rhizomes outperform contact-only injury on perennial plants, but turf selectivity varies sharply by species and site. Control border populations before they seed or move into managed turf.

Choosing a Turf Herbicide

Perennial weeds often regrow from stolons, rhizomes, tubers, bulbs, or deep roots. Select a product labeled for the desirable turf and target weed, treat actively growing plants, and plan the complete sequence of repeat applications or renovation steps allowed by the label.

Research and label note: University research may discuss treatments or timings that are not permitted on every turf species or use site. Research evidence does not expand a product label. Confirm the desirable turf species, use site, target weed, application timing, rate, adjuvant directions, and reseeding restrictions on the current label before use.

University sources: University of Georgia Extension: Weed Control in Home Lawns.