A little lawn sense
When should I put down pre-emergent in Ohio?
Apply crabgrass preventer before seeds germinate, often in April in Ohio. Check local soil conditions instead of treating a date as a guarantee.
Watch the soil
Crabgrass begins germinating around sustained soil temperatures of 50 to 55°F. A soil thermometer and local Extension updates help you act before emergence. Southern lawns reach that point earlier.
Check your seeding plans
Most pre-emergents also interfere with lawn seed. Read the reseeding interval before treating a thin lawn you intend to seed.
Apply only where needed
Use a product labeled for your grass and target weed. Calibrate the spreader and water in exactly as directed. Existing weeds generally need another approach.
Questions from the yard
Is one warm afternoon the signal?
No. Watch sustained soil conditions and local guidance.
Will pre-emergent kill large crabgrass?
Most products do not; they mainly prevent new seedlings.
Sources & further reading
Reviewed October 2026. General US home-lawn guidance; local recommendations may differ.