This is the one lawn service where timing decides the outcome. Cool-season grass — fescue, rye, bluegrass — is aerated and seeded in early autumn, when soil is warm and weeds have stopped competing. Warm-season grass is done in late spring. In the opposite window the seed germinates into heat or frost and most of it dies, which is why people conclude overseeding does not work. We will tell you which grass you have and which month is yours, even if that means booking you for next season.