Well, I finally did it...overseeded the 10-month-old TTPR/KBG lawn with TTTF and KBG...and it worked! So it can be done...but read on to find out how I did it...I was quite careful due to what people on here had told me about the PR messing with the germination of other seed due to allelopathy. I did this a little over a month ago now. I actually prefer the lawn consisting of a mixture of these three species, guess I'm odd since no one else here seems to like that three-way mix). We're at ~4.5 weeks now. The existing PR thankfully did not prevent or delay germination of the new seed. The TTTF started to come up within 6 days, and was fully up in about 3 weeks time. The KBG just started coming up last week. Perhaps it wored so well because the PR was only 10 months old. Or b/c it got heat stressed. Or b/c I mowed it to ~1.8 inches before hand on the last mowing before starting the project. I also thinned the lawn fairly drastically prior to over seeding, by utilizing heavy core aeration (three passes) and also verticutting (two passes). I brought up a lot of dead and living grass in the process. I'm currently touching up the few spots that need it with a little extra seed. Here are some photos of the project (same area plus or minus a foot or two) at the various stages for reference (I do consider it a successful outcome even if it was my first time doing it and I learned a lot!): The top photo is the before photo, taken on 8/17/12. The middle photo is about ten days after overseeding, on 8/29/12. You can see the existing PR and KBG, and the TTTF was in the midst of germination, but is hard to see in the pic. And the bottom photo is from 9/21/12, taken right after the first mowing and application of starter fertilizer (I decided to hold off on the fertilizer until after germination so as to slow the growth of the existing grass to prevent it from overtaking the new grass. I'm glad I did this). Here is what I used for overseeding: -TTTF (approx 75% Firecracker LS and 25% Bullseye) -KBG (approx 33% each of America, Bewitched, and Rugby II) -A low amount of the existing TTPR seed blend (see below) was mixed with the fescue and KBG seed; I only used this in those areas that were really bare after the verticutting/raking. In this way, I created a uniform lawn in the bare spots that blended with the old grass. (The existing lawn prior to overseeding was a blend of KBG and three cultivars of TTPR sourced from from Allied Seed: ASP6005, ASP6002, and ASP 6001.)

I disagree with Auteck's recommendation, and I'm a little surprised he recommended what he did. Your original grass seed mix selection was tall fescue, fine fescues and KBG. I suspect you have mostly tall fescue growing since you have bare spots. If the KBG in your original grass mix had germinated fully, then it should fill in bare areas in the sunnier parts of your lawn. I agree with him in that perennial rye is usually what is grown in your area, but there was no perennial rye in that original mix. Overseeding your lawn with it now will give you some throughout the whole lawn, but the bare spots will be all PR, and they will stand out against the TF you have now. My advice, use either all TF to overseed, or a mix that has similar percentages to your original mix. I would also stick with Pennington's as it is usually the best mix in the big box stores.

Hi John, thanks for responding. I did think initially that it was something to do with the hot weather, but I am still leaning towards the leaf spot / melting out. In one of the areas it started a month or so ago before the hot weather really kicked in. I did see some information about the possible alleopathic affects of PRG on other grasses, but I'm not really sure how that would impact the fine fescue that I have already or any new seed I might overseed with. It seems like a lot of store bought mixes include PRG along with KBG or fescues. If PRG was that bad I don't know why they would include it in the mixes. Then again I know store bought stuff is not always the best. Does anyone else have any thoughts on what would blend well into predominately fine fescue lawn?

I am finalizing my plans for overseeding. I have decided to rent a slice seeder for overseeding. Anyone have any advice before I do? I assume I need to flag my sprinkler heads and avoid them? Seed of choice for this year is: I broadcast sprayed yesterday with a good amount of 2D4. Any other suggestions? I have a particular weed that I can seem to get rid of, I'll follow up later with a few pics of this weed for advice. It's a clump of crab grass that has migrated all over the front yard.