OK, I live in moderate Maryland. My poor neglected lawn has both bare spots and weeds. When should I put down the pre-emergent weedicide and when should I put down seeds?
Pre-emerge is exactly what it says - it works by preventing germination - so you don’t want to apply that until your grass seed has been incorporated and is off to a good start.
Do you have a county extension office in your area? In Nebraska the pre-emergent goes down after the forsythia blooms but before the lilacs bloom.