Johnson Grass

About Johnson Grass

Johnson grass (Sorghum halepense) is a tall, aggressive perennial grassy weed that shares the same origin story as dallisgrass in Middle Tennessee: it arrived in construction straw used during post-build overseeding. It is concentrated in Spring Hill and newer construction areas, and homeowners almost always misidentify it as crabgrass. Johnson grass is classified as a noxious weed by Tennessee seed testing — a stricter classification than dallisgrass — but it still shows up regularly in cheap seed and construction straw. Johnson grass is rhizomatous, meaning it spreads underground from root pieces, not just from seed. It grows fast and tall, easily outpacing fescue mowing height within days of cutting. It is a warm-season perennial that becomes visible in late spring but has been established in the soil since the previous year. Like dallisgrass, it is a monocot — the same grass family as your desirable fescue — which means post-emergent selective herbicide options are extremely limited. Glyphosate (Roundup) provides temporary suppression but Johnson grass has developed significant resistance in many areas. The plant bounces back, but the tall fescue you killed alongside it does not — leaving ugly bare patches in your lawn. The right approach is the perennial treatment timing flip: treat in late summer and early fall when the plant is actively pulling nutrients down into its root system for winter dormancy. Herbicides applied during this translocation window ride along into the roots and cause real systemic damage. Do this for two to three consecutive years while maintaining thick, competitive fescue, and you will eliminate it. Mr. Lawn Care includes Johnson grass control at no extra charge as part of the standard lawn care service plan — a two-to-three-year commitment that most companies will not make because it requires patience and does not fit a single-season billing model.

Johnson Grass (Sorghum halepense) is a turf weed commonly found in lawns throughout Middle Tennessee, including Columbia, Thompson's Station, Spring Hill, and the surrounding areas. This entry is part of our Weed Identification Guide.

As lawn care and treatment specialists, we identify and treat Johnson Grass regularly when servicing properties across the region. Proper identification is the first step toward selecting the right herbicide and timing for effective control.