· by Michael Blair, Nashville's Weed and Feed
Most lawn weeds in Middle Tennessee fall to a standard broadleaf herbicide applied at the right time. Two do not, and they are the two that generate the most frustration, because repeated applications of the wrong product look like the product failing rather than the wrong product being used.
Nutsedge is not a broadleaf weed at all
It is a sedge, which is a different plant family from both grasses and broadleaf weeds, and broadleaf herbicides have essentially no effect on it. It is recognizable by a stem that is triangular in cross section, by leaves in sets of three, and by growing noticeably faster than the surrounding grass so it stands proud a day after mowing.
It also reproduces from tubers, small nutlets on the roots. Pulling a plant leaves the tubers behind and each one produces new shoots, which is why hand weeding usually multiplies it rather than reducing it.
What kills nutsedge in a lawn?
A herbicide specifically labeled for sedge control, applied to actively growing plants in warm weather. Products based on halosulfuron or sulfentrazone are the common choices, and they translocate to the tubers rather than only burning the visible shoot.
Timing matters: treatment while the plant is young and actively growing is far more effective than treatment on a mature stand late in the season. Expect to repeat, because tubers emerge over time. And fix the cause, since nutsedge thrives in ground that stays wet, so a persistent patch is often marking a drainage problem.
- Triangular stem and three-ranked leaves identify a sedge
- Broadleaf herbicides do not touch it
- Use a sedge-specific product on actively growing plants
- Do not hand pull, which leaves and spreads tubers
- A recurring patch usually indicates poor drainage
Wild violet is a broadleaf that shrugs it off
Violet is a genuine broadleaf, and the problem is the leaf. It carries a thick waxy cuticle that sheds herbicide before enough is absorbed, and it spreads by underground rhizomes as well as by seed, so killing the top growth leaves a network that regrows.
It also prefers exactly the conditions much of Nashville offers: shade, moisture and heavy clay. A violet problem under a tree is partly a lawn problem, because thin grass in shade gives it the opening it needs.
What kills wild violet?
A three-way broadleaf herbicide with triclopyr in it is the usual recommendation, applied with a surfactant so it stays on the waxy leaf long enough to be absorbed. One application will not finish it, and the plan should assume several across a season and probably into a second year.
Autumn is the better window. As temperatures cool, perennials move resources down into the roots and rhizomes, and a systemic herbicide applied then goes with them. The same product on the same plant in July mostly burns leaves that grow back.
FAQ
Getting Rid of Nutsedge and Wild Violet — questions
Why does nutsedge come back after I pull it?
Because the plant grows from tubers on the roots, and pulling the shoot leaves them behind while breaking dormancy on others nearby. Each tuber can produce a new plant, so hand weeding an established patch generally increases it. A sedge-specific herbicide that moves down to the tubers is what actually reduces the population.
When is the best time to treat wild violet?
Autumn, once temperatures have cooled and the plants are moving reserves into their root systems, because a systemic herbicide travels with them. Spring treatment has some effect and is far less reliable, and midsummer applications in Middle Tennessee heat mostly damage leaves without reaching the rhizomes.
Will improving the lawn crowd these weeds out?
It genuinely helps with violet, which exploits thin turf in shade, so overseeding, correcting mowing height and addressing soil compaction all reduce the opening it needs. Nutsedge is less responsive to competition and more responsive to drainage, so the equivalent step there is fixing whatever keeps that area wet.
How does nutsedge spread?
Mostly underground, through tubers, the small nutlets that form on its roots. Every tuber can send up new shoots, which is why one plant becomes a patch. It favors ground that stays wet, so a spreading stand often marks poor drainage, and a sedge-labeled herbicide that travels down to the tubers is what thins it.