What time of year is right for seeding grass? I live in Tennessee and had always thought that February was the best month – or March at the latest. A landscaping firm that I don’t fully trust wants to seed my yard in September or October and do four fertilizer applications beginning now.
I’m really very ignorant on this subject and need your input but I give them the go-ahead.
The generally recommended period to sow grass is after the August heat, but before the frost. The typical weather at that time–days that are not overly hot and nights that are cool–along with shorter daylight hours, permits root growth without either encouraging excessive leaf growth (outstripping the roots) or simply burning up the leaves. Once the grass has germinated, applying fertilizer with low nitrogen and higher phosphorous and potassium levels further promotes root growth so that when the Spring arrives, the grass has a developed root system to support the high nitrogen fertilizer to grow the leaves as well as the higher temperatures and longer daylight periods that also promote leaf growth.
In an area where the ground does not freeze solid over the Winter, I could see where one might go for a late Winter/early Spring sowing, simply pushing the root growth to the opposite end of the Winter, but that is not the “traditional” method.
Early fall is the best time to sow grass seed in most parts of the country for reasons Tom cites - also the soil is relatively warm and there is generally more rainfall to promote good grass growth at that time of the year.
If it’s more convenient for you, early spring seeding can also work fine.
I agree with everything Tomndebb said. For your region Zoe if you want to spot treat your lawn now you can do so, however, taking into account migratory birds, rain, etc…etc…I’d heavily hay the spots if that is what you wish to do.
Are you looking to grow area right now? If that is part of your question, then the answer is yes, you can do that right now. But generally speaking for normal seeding what Tomndebb said is the way to go.
Yes, big seeding job is best left to Fall. One important reason, among other good ones given, is that distrubing the soil in Spring is going to create a haven for weeds, which can thrive in tough conditions that are coming up. Weeds will over run you, and you weak/immature lawn will wither in the heat and succumb to disease. It won’t be able to reproduce much either when Fall comes.
Nature seeds in Fall: Weeds are on the way out, your new grass plants have optimal conditions, and when Winter sets in, the weeds are whacked naturally… and when properly fertilized, your grass will use its dormant time to batten down the hatches and store up a burst of energy. When the next Spring breaks, you new grass is ready to compete with the weeds and is mature enough to survive drought and disease. And, your grass will be able to reproduce, which is important when you are chopping off the top every 3-5 with a mower.
Good point! Can’t question with Mother Nature.
You can question Mother Nature, it’s just not nice to fool her! 
A good fertilizer program can fill in a lawn nicely. Once the lawn is thick with grass, you don’t get a large weed problem every year either. You have to sow dead spots now. Who wants a big bare spot all summer. It sounds like you’re planning to seed a thin lawn, so wait for fall. Them killing of the broadleafs now will help greatly for the overseeding in the fall if that’s what you’re doing.