It sure would.

If you killed off the lawn in order to reseed, then you should definitely rake it up before reseeding. The seed won't be able to get down to the soil with a layer of dead grass on top. If you killed off a lawn area to make a flower bed etc, leaving the clippings would be fine.

I'm wondering the same thing. I'm debating whether I'm even going to mow it low. It's so dead and fallen over that I don't know that mowing would even do anything. Organic matter, yes, but it should also keep the seed from washing away and eliminate the need for topdressing/mulching? How thick a layer of dead grass is too thick? I guess the fear of not raking is that you have too dense a layer on top of the seed for the new grass to come through? Also, if the dead grass is too thick, it will lessen the seed to soil contact? Curious what some of the regulars have done , morpheus, turftoes, etc., did you guys rake most of the dead grass up?
Parafly, are you aerating then broadcasting or are you slitseeding?

Raking would help. What you want is good soil contact for your seeds. It would make good ammendment to the soil if you can wait a long time for it to decompose

I'm slitseeding, which is why I think it's less important if I rake it all up.

Please...do yourself a favor and rake. I didn't. Bad move. I had to fix that.

Actually, it was easier to dethatch and then mow it up, and a lot faster, too.

I'm a bit torn as I fear I have lost my fescue back yard this summer but am not actively trying to kill it of course. Its still pretty thin and I was planning on just mowing low and bagging that up. Sound like a plan? Seems how well you aerate afterwards is a factor as well?

Allow me to further clarify my original response: Leaving the grass should be OK, so long as it isn't long, and covering the soil that the seed should be in. If you scalp the existing grass before seeding, or use a slit seeder, you should be fine. And you can then take advantage of that decaying organic matter. :-)

I dont' have a bagger and I can't justify another $450 to buy onoe for my mower - I've spent enought money on this project already! (going to be ~ $700 - $800 by the time its done)

Here's an Idea. What if you power rake or dethatch all the dead grass. Keep it on the side. Seed then throw 1/4" of the dead grass on top of the seed?

I agree with dlenart. I did this last year and had excellent results and I didn't need to spend any money for a top dressing. I used a power rake set at the deepest setting, (which helped level out some bumps I had as well). I raked everything up, slit seeded and then covered with the old grass. This was a lot of work, but I had better results as the year before I just mowed it down as low as possible and left it.

As a side note, I still had a pile of grass that composted and I'm growing pumpkins in it for my daughter and they are growing out of control!

Very interesting idea dlenart. That's what I'm going to do then. Rent a dethatcher for like $24 for 4 hours, rake it up, and then save it for use as a top dressing. That saves from having to buy more straw too. Jcsogove, do you remember how deep the lowest setting was? 1/2 inch? When dethaching that deep, will there still be some of the old grass still in place or does that basically take you down to bare dirt? I'd rather still have a little dead grass in place. Parafly, is renting a dethatcher doable for you?

Very interesting. I assume you guys are cutting low for reseeding purposes as opposed to renovating? Are you dethatching (Fescue) b/c its mostly all died in the heat?

I don't think it was quite 1/2" deep and there was some grass left, but not very much. It was some of the better fescue patches that were rooted pretty good. It left a nice loose soil. I think that would have been fine to seed right on that, but my wife remembered all the nice little slits and how the grass grew first out of those and made me get a slit seeder before I dropped the seed.

weigojmi-I had sprayed Roundup and cut it down as low as I could but I couldn't get very low due to the uneveness of my backyard so I got the power rake/dethatcher.