Overseeding a weedy lawn will not kill weeds on its own. However, thick grass growth produced by overseeding prevents new weeds from sprouting. In order to keep your lawn weed-free with overseeding, first, kill any existing weeds, then prep your lawn and spread new grass seed.

Should I kill weeds before overseeding?

It is best to kill weeds first before overseeding. Weeds like bare spots and can continue to spread and invade your lawn if you don't do anything about them. That's why overseeding helps control them by making your lawn thicker and fuller, and able to choke out weeds.

How do you overseed a lawn full of weeds?