You don't need to mulch new seed. There are some regions of the country where it is very popular, but grass seed scattered on the surface, and then pressed into the surface by a roller or someone walking on it, will be fine. The mulch helps to keep the seed moist. Pressing it into the soil helps, too.

Okay. That's a relief. Thanks. Since I already bought the moldy straw, though, should I use it? Or will it spread to the new grass?

Can't get the pictures to load. Try this:

I would not use it, but I would not use it if it was great straw.

Thanks. Would you use something else to keep the seeds moist? Just water frequently?