Q.When to sow grass seed?
I live in SW MO. We have had our first killing frost. Can I sow grass seed now or will I have to wait until spring?
Grass should have about 6 weeks of growth before a killing frost. Sowing in early September is a popular time but spring is good too. It is too late for grass to form sufficient roots to make it through winter in MO. Sow seed as soon as you notice the grass starting to green up next spring. New grass needs as much time as possible to get established before brutal heat arrives. You may need to water the new lawn during dry or very hot spells to make sure it makes it through the summer. Here are details on growing grass in Missouri: https://ipm.missouri.edu/MEG/2014/5/Seeding-and-Fertilizing-Missouri-Lawns/