Can you put grass seed over an existing lawn that is full of weeds? And will the new seed kill out the old grass and weeds?
Certified GKH Gardening Expert
This is a practice called overseeding. Yes, you can do it, but whether if takes over the old grass and weeds depends on what kind of grass it is and what the conditions are.
In most cases, it will not push out the weeds because the conditions that cause the weeds to thrive still exist. You need to correct these before you overseed. This article may help with that:
Some grasses are more aggressive than others. If you overseed with a more aggressive grass, it may push out the old grass. But, if you overseed with a less aggressive grass, you will see no change.