Question
Hi Ronald,
  My lawn guys put a granular slow release fertilizer down on August 23 of this year & was going to spot spay any weeds. I noticed he didn't spray any weeds at that time. Can I start planting grass seed now in Sept?

Thanks for your time,
Have a nice day!          
         Beth

Answer
First of all, make quite sure that he did not use a "Weed and Feed" product. If he did, you must wait before seeding or sodding.
If he used a straight fertilizer, you can go ahead and plant the grass seeds; but you still have to deal with the weed problem. When you plant the grass seeds, you will have to water regularly for the seed to germinate. This will cause the weeds to grow even more.
What's to be done?
If the weeds are bad in patches, you can use Round Up?to kill off the patches and then replant these areas.
If the weeds are not concentrated in patches and you think that the new grass seedlings can grow through them, then you can apply a pre-emergent weed killer and wait out the time before planting (see the label!). Most pre-emergent products work by killing new roots from seeds.
And they do not know whether a root is from weed seeds or from grass seeds.