Where are you and what kind of grass do you have? Zone 8 only tells us the coldest you usually get during the winter, but nothing else. Most people think of zone 8 as being really hot, so expect a warm season grass, but the Seattle area is also zone 8 (mild winters) and cool season grasses do best.

The answers to your question depend largely on where you are and what kind of grass you have.

As Bill indicates where you are is important and since another forum of interest for you is Pacific Northwest I would guess you are in that area.
1. Grass seed, to germinate properly, needs to be in contact with soil. Scratching the soil before overseeding would be a good idea.
2. There is no really good reason to mow low prior to overseeding, and doing that could do more harm to the grass that is growing there than would help.
3. Always wait to feed until the grass is up and growing.
A lawn may be off color for reasons other than low Nitrogen levels. Soil pH, other nutrients not in balance can interfere with a plants abilty to uptake, or utilize, many other nutrients.
So, what is your soils pH? How much organic matter is in that soil? What kind of life do you see in your soil? What does that soil smell like?

2. There is no really good reason to mow low prior to overseeding, and doing that could do more harm to the grass that is growing there than would help.

Have you ever overseeded before? LOL. The reason for mowing low[er] than usual, is so that you don't have to get back out there and mow again before the new seed has matured. If you don't, and need to get out there and mow, you'll do much harm to the young seedlings. That negates the whole reason you're overseeding.

Yes, Im in the PNW (WA) coastal area. It was hydroseeded with fine fescues and I'm planning on overseeding with a mixture of three ryegrasses (grown in Oregon).
The topsoil is virgin mixed with some other local soil brought in to raise and level the area. Don't know the PH--probably on the acid side.
I haven't had much of a chance to add any organics yet but I plan on using soybean meal and or alafalfa at a later date.
I thought you should mow low so the seed has a better chance of touching soil, since the existing grass is growing well and I wouldn't want to have to mow and displace the seed any sooner than I had to.
I've been weed popping the unwanted grass species and broadleaf weeds and I'm seeing some good sized worms! Yay!

This just In:
I called Milorganite and they said their product could be put down immediately before overseeding, immediately after overseeding or it could be actually mixed with the seed.

Thanks for all your help!

If the grass you put in last year is fine fescue, go easy on the fertilizer. Use about half the recommended rate because fine fescue not only doesn't need as much fertilizer as other grasses but can suffer if it gets too much.

There are a couple of reasons to mow low before overseeding. One is to make it easier for the grass seed to make contact with the soil and another is to give the new seed a chance to germinate and start growing before you mow. Mowers create a slight vacuum effect and can pull new seedlings out if you mow too early.

Another reason to mow low is if you want the new grass to out-do the existing grass. If that's the case, scalping all at once can cause a lot of stress to the existing grass and may even kill some of it. If you like the existing grass and are just trying to supplement it, you want to gradually lower the mower deck so that you cut the grass low, but you don't shock it.

A couple of other things that can improve the seed-to-soil contact are either core aerating before seeding, or renting a slit seeder. The slit seeder will help get the seeds into the ground so that they're less likely to be pulled out if you mow before the grass is firmly rooted.

Since you're seeding rye, the concerns about the new grass growing enough are less of an issue (rye germinates very quickly).

I have an AG Fab tow behind slit seeder that I've never used--plus all the weed popping I've been doing has aerated the ground quite a bit!

Sounds great, I really appreciate it!

skizot, when you cut your grass blades really short you eliminate the necessary ability of those grass blades to take in the sunlight and manufacture the necessary nutrients the grasses roots need to grow and produce more grass plants. Cutting grass short is a major mistake at any time.

kimmsr, I'd really like to know your take on overseeding then. You've either never done it before, or you don't understand how fragile the new grass seedlings are. bpgreen touched on just one of the reasons why you don't want to have to mow the existing grass before the new grass has matured enough; suction from the mower. I'll list all that I can think of:

1. Suction from the mower can pull the shallow rooted seedlings from the ground.
2. If the seedlings aren't rooted well enough, the blade can actually rip them out of the ground.
3. Walking on the new seedlings, and running over them with the mower will kill them.

All three can and will occur if you have to get back out and mow too soon. So, if you're not going to cut the existing grass low, what's the point in overseeding at all? You're just going to end up wasting your time and money overseeding. Scalping will stress the grass, and possibly kill some of it. That is not what I'm suggesting. bpgreen already hit on the point I'm about to make; you gradually cut it lower, and then you overseed.

I'm curious, too, kimmsr. I've never reseeded anything so what I think I know is what I've been reading here over the years. The generally accepted order of events (with some exceptions) is as follows:

2. Scalp the grass to expose the soil and seeds to the sunlight. I like the idea of gradually lowering the grass height but that is not the common custom.

3. Apply seed

4. Roll it down and/or cover with [your favorite top dressing].

5. Water for 10-15 minutes, 3-4 times per day, for 2-3 weeks to germinate the seed.

6. Mow normally at the mower's highest setting. When the new grass is tall enough to be mowed, the new roots will be deep enough to prevent them being pulled out of the ground by the mower.

7. After the grass has 1) 80% germinated, or 2) been mowed 2 times, back off on the watering frequency and increase the watering depth (time).

There are variations on all of that but not much variation on scalping or lowering the grass height at the beginning. I believe the rationale for scalping is to expose the new seedlings to as much sunlight as possible so they can start to photosynthesize and grow roots. kimmsr, what is your thinking for not scalping or lowering the grass height?

I might add that in Nature (not to be confused with normal agriculture), hoofed animals do the reseeding. The knock seeds off the grass plants they are eating and press the seeds into the ground with their hooves. At the same time they eat the grass down from many inches/feet high to an inch or two. Forage types of grasses usually grow with some space in between the plants so there is more sunlight in most all cases.

Thanks, all.

1. You should not need to reseed any grassy area that grows grass tall enough to need mwing and thick enough to cause concerns any seed would not reach the soil.
2. Scalping grass so limits its ability to manufacture nutrients that the grass will then allow weeds to grow in that area.
No matter what some "experts" of the synthetic school of thought say about overseeding a lawn it should not apply to an organic lawn.

kimmsr, wow. I see why many ignore your advice. What you've just said makes very little sense at all. Don't reseed a thin area in a cool-season lawn (TTTF, not KBG)? Then you go on to say that cutting low allows weeds? The former of those two will allow far more weeds to grow. Also, overseeding is not a synthetic vs. organic thing, and it's misleading to post that it is.

It seems that you like to throw around your synthetic vs. organic blabber, and have very little substance to your posts.

skizot, go back and reread the part that comes after "...need mwing and..."

I wonder if any of the schools have studied the seed germination and rooting performance of scalping versus not scalping when reseeding? It could be that the preparation of the grass and soil prior to scalping helps the grass plants return from the scalping. On another forum, xproud describes a method for leveling a bermuda lawn that I was sure would kill his entire lawn. However, he went to an extreme to prepare the turf before the final scalping. Another possibility is that you're working with percentages. A certain percentage of the old grass plants will die and a certain percentage of the seeds will germinate. It is pretty well known that you usually get some weeds when you overseed but again you might be working with percentages.

Just because everyone has done it that way for centuries, that does not make it right. That's my philosophy on plowing fields.

I also think the movement toward lawns that do not mix KBG with fescue is a mistake. Fescue makes a hard lawn to handle simply because it needs one seed per plant. If a plant dies, then you have a bare spot that will be bare until another plant is planted or some other plant sweeps in - like KBG.

dchall, sorry. Maybe you have a better understanding of what he's trying to say.

I think we should get back on track here and look at the OP's situation. The OP lives in the PNW and probably has too much moisture for KBG and tall fescue. I think the most prevalent grass for that area is perennial rye and some of the fine fescues would work, also.

The OP hydroseeded a fine fescue mixture last fall and has some perennial rye to overseed this spring.

All the fine fescues are bunch grasses except for creeping red fescue, which spreads relatively slowly. Perennial rye is also a bunch grass. Odds are good that overseeding will be needed every few years to keep the lawn full since the only spreading grass in the mix is creeping red fescue and A) it's probably a small percentage of the mix and B) it spreads relatively slowly.

Scalping is probably much less necessary in this situation since fine fescues are slow growing and perennial rye is quick to germinate and establish. Perennial rye will germinate in 3-5 days so if the fine fescue is mowed a little shorter than usual, the lawn would probably be ready to mow in 2-3 weeks.

bpgreen could be right about the rye. Catkin, what kind of grass do your neighbors seem to have success with?

skizot, he was saying that if the grass is tall enough to mow, AND it is so dense that new seed will not fall all the way to the soil, then why bother with reseeding?

dchall, I assumed he was saying something different. If it's so dense that the new seed won't fall all the way to the soil, then that's pretty much a no-brainer. I don't think anyone would be asking about overseeding, or even contemplating that, if their turf was that dense. Hence the reason I assumed he was talking about something else.

Sure, I agree. The OP at first posted that the grass was sparse and later posted this, "I thought you should mow low so the seed has a better chance of touching soil, since the existing grass is growing well and I wouldn't want to have to mow and displace the seed any sooner than I had to." Thus the confusion on everyone's part.

Yeah, I assumed "the existing grass is growing well" didn't negate the fact that he has thin areas; it just means that the grass that is there, is growing well. :-) Implying that it will continue to grow well when he attempts to overseed, causing problems if it needs to be mowed before the new seed has germinated and matured enough. Those are just assumptions though. :-)

It never ceases to amaze me how the preconcieved notions of many people preclude any other concept.
Why does grass have green blades and why do some of use tell people to mow high?
Grass has green blades so those grass blades can absorb sunlight and through photosynthesis manufacture nutrients that will feed the plants roots so htose roots can send out more plants to grow more grass. Cut the green grass blades off and you stop that process greatly harming the grass plant. Scalping growing grass is never a good idea.

The OP has fine fescues and has thin areas. He wants to add perennial rye to the lawn. Most fine fescues are bunch grasses. The exception is creeping red fescue, which spreads through rhizomes, although slowly. Overseeding is probably a good idea, since it's not going to fill in very quickly on its own.

Since fine fescues grow relatively slowly and rye germinates and establishes quickly, scalping is probably not as necessary as it would be if he had a tall fescue lawn and was overseeding with KBG (tall fescue grows quickly and KBG germinates slowly). I'd probably still mow lower than usual to give the rye a little more time, but as long as it has about 2-3 weeks between seeding and the first mowing, it should be okay.

Depending on how much of the fine fescue is creeping red, you may need to overseed periodically to keep the lawn full.

Cut the green grass blades off and you stop that process greatly harming the grass plant.

You don't stop that process, unless you cut ALL of the blade off. The grass is stunted, yes, but it's temporary. I still don't think you know what's being discussed here, kimmsr. No one is saying always cut low, and no one is saying lower your cutting blade to the dirt. Those are your assumptions that no one else shares reading this thread.

kimmsr, by the way, you never explained your method for overseeding, you just gave some comment about how no one should ever have to overseed. I don't know about others, but I'm still waiting for your procedure.

I see no good reason to "overseed". If you make the soil you are trying to grow grass in into a good, healthy soil the grass you have will grow and fill in any bare spots. If the soil is not one that grass will grow in really well "overseeding" will not fill in anyway.

Greetings!
skizot---B*I*N*G*O!
"Yeah, I assumed "the existing grass is growing well" didn't negate the fact that he has thin areas; it just means that the grass that is there, is growing well. :-) Implying that it will continue to grow well when he attempts to overseed, causing problems if it needs to be mowed before the new seed has germinated and matured enough. Those are just assumptions though. :-)"

The hysdroseeder simply didn't put down the mixture thick enough.

I've no intention of scalping the lawn.

I was asking if it should be mown on a lower than normal setting so as to expose some soil for the seed to land in.

I have a small window of opportunity coming up. Just my luck they'll change the forecast and I'll have to water !

The fast germination of the ryes was what I was hoping for.
There's so much other work to be done in the garden.

Thanks again, everyone!

Catkin--With PR's fast establishment and fine fescue's slow growth, mowing lower than normal should be fine.

Perennial rye is a bunch grass and so are all the fine fescues except for creeping red fescue. So the only grass in your lawn that will spread at all is the CRF. This is not a function of the soil, but a function of the grasses in your lawn. Bunch grasses don't spread even when the soil is healthy.

If you've got enough CRF in the fine fescue mix you put in last fall, it may spread enough to keep the lawn full once you get it into good shape to start. CRF doesn't spread as aggressively as KBG does, so I think your plan to overseed now is probably a good idea. In the future, if the CRF doesn't make up enough of the mixture, you may need to overseed again. Fine fescue doesn't germinate quite as fast as rye, but it germinates much faster than KBG so if you need to overseed in the future, you can probably still avoid scalping, but you'll probably want to mow lower to give the new seeds a chance to establish before the existing grass needs to be mowed.

Good luck, and keep us posted on your progress.