I think that would be wise, around day 15.

j4c11,

If we wait to apply starter fertilizer until day 15, don't you think we will be trampling on the new grass during application. I just had a small area (around 400 sqft) re-seeded from scratch with KBG. Even after 21 days and watering every 4 hours the seeds are just germinating. I applied my fertilizers during the seeding. I applied both Milorganite and Scotts starter fertilizer. Although few weeds have popped up along with the grass seeds, I am reluctant to step on the grass to pull out the weeds in the fear of trampling the new grass.

PSU4ME

I also live in Mass and a co-worker is doing a lawn reno and he is struggling with what type of grass seed mix to use.

It sounds like he has one area of full sun and another area of sun and shade.

If you don't mind me asking; what blend of KBG did you buy and where did you purchase it from?

Thanks

The reason for putting starter fertilizer down at seeding is that it avoids walking on the seedlings when applying it at the optimal time. Starter is not needed for germination, but it is advantageous to the growing seedling, and its undeveloped root mass, to have easily available PK (and N) for growth.