How to Fix a Lawn Full of Weeds

Transform a weed-infested lawn by identifying weed types, applying targeted treatments in spring or fall, then overseeding and maintaining proper care to establish healthy grass that naturally crowds out future weeds.

1. Know Your Enemy First. Walk your lawn and identify the dominant weeds. Broadleaf weeds like dandelions and clover have wide leaves, while grassy weeds like crabgrass look similar to grass but grow in clumps. Annual weeds die each year and return from seed, while perennial weeds have deep root systems that return each season. Take photos of problem areas to reference when selecting treatments.
2. Pick Your Battle Plan. For lawns with 50% or more weeds, consider starting over with complete renovation. For moderate infestations, use selective herbicides that kill weeds without harming grass. Apply pre-emergent herbicides in early spring to prevent annual weeds from germinating, and post-emergent herbicides when weeds are actively growing. Organic options include corn gluten meal for prevention and vinegar-based solutions for spot treatment.
3. Spray Smart, Spray Safe. Read all label directions carefully and apply on a calm, dry day when no rain is expected for 24 hours. Use a pump sprayer or hose-end sprayer for even coverage. Treat broadleaf weeds when they're young and actively growing, typically in late spring or early fall. For grassy weeds, apply treatments when soil temperature reaches 55-60°F for several days. Avoid treating during drought stress or extreme heat.
4. Let Chemistry Do the Work. Most herbicides take 7-14 days to show results, with complete die-off occurring within 2-4 weeks. Avoid mowing for 2-3 days after application to allow proper absorption. Dead weeds will turn brown and begin to shrivel. Resist the urge to rake immediately, as this can disturb the herbicide's effectiveness on root systems.
5. Clear the Ground Clean. Once weeds are completely dead, rake out the debris and dead plant material. Use a dethatching rake or rent a power dethatcher for large areas. Test soil pH and amend if necessary - most grasses prefer pH between 6.0-7.0. Add compost or quality topsoil to thin areas where weeds left bare spots.
6. Sow the New Lawn Now. Select grass seed appropriate for your climate and lawn conditions. Cool-season grasses like fescue and bluegrass should be seeded in early fall or spring. Warm-season grasses like Bermuda and Zoysia are best planted in late spring. Spread seed at recommended rates, rake lightly to ensure soil contact, and cover with a thin layer of starter fertilizer.
7. Feed the Future Lawn. Keep seeded areas consistently moist but not waterlogged for 2-3 weeks until germination occurs. Water lightly 2-3 times daily rather than deep, infrequent watering. Once grass reaches 3 inches tall, begin normal watering schedule of 1 inch per week. Apply starter fertilizer according to package directions and avoid foot traffic until grass is well-established.
8. Build a Weed-Proof Lawn. Maintain thick, healthy grass through proper mowing, fertilizing, and watering to naturally prevent weed establishment. Mow at the highest recommended setting for your grass type, fertilize 2-4 times annually, and water deeply but infrequently. Apply pre-emergent herbicide each spring before soil temperatures reach 55°F to prevent annual weeds from returning.