Q: What's the best time of year to plant grass seed? And should I seed and fertilize at the same time?
— Rick, Seymour, CT
A: Roger Cook replies: In much of the country, grass seed is best planted before or after summer. That's primarily because it's almost impossible to keep new seed moist in the summer without nearly constant watering. The other problem with summer planting is that the soil prep work opens up the area to weed seeds, which readily germinate in the heat. (If you simply must plant in hot weather, mulch the planting area with a light layer of peat moss or similar material to prevent the seed from drying out.)
Where you live, and throughout much of the northern half of the U.S., early fall is the best time for sowing grass. The soil is warm, but daytime temperatures are moderate, making watering less of a problem, and the weeds won't grow. I'll start seeding in the last week of August and will push into the first week of October if I have to. By the cool days of late October, the new grass should be fresh and thick and strong enough to survive the winter.
Apply a starter fertilizer when you sow the seeds, and then add more fertilizer three to four weeks later. That's necessary because all the watering you do to make the seeds sprout actually leaches the first application of fertilizer out of the top layer of soil, putting the rest beyond the reach of the young roots.