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.)

Bark? Is that shredded bark all over the lawn? Yes, rake that up. Don't worry about your present soil. And don't bring in ANY new soil. Two inches is a big mistake. The only time you need new soil is when you need to change your drainage. Because new soil WILL change your drainage. New construction should have perfect drainage by design. You'll only be screwing it up by adding more soil. You can fix your soil with your first application of alfalfa pellets. If you want to speed up the process, spray some molasses at the same time. 3 ounces per 1,000 square feet is a good start. If you are worried about your soil chemistry, get a test at Logan Labs and write back here to share the results. Rye is an excellent choice for the PNW. Seems they have the perfect climate for it. Rent the roller to roll over the seed once it is down. That ensures you have the best seed-to-soil contact.

Wow, I was surprised to see this thread still alive. Here's the recap on what happened last year: The 2007 June-July-August heat and drought combined with a vacation basically killed the TTPR after it had been fantastic in the fall and spring, so when I was deciding whether to repeat the experiment by overseeding (really starting over) in year 2, I decided to change to the more drought/heat tolerant TTTF and try to find some cultivars with a thinner blade and dark green color. Of course, this spring of 2008 has been plenty wet and not too hot thus far, so any cool season grass would likely be doing very well at the moment, as is the TTTF. I will try to post some pictures soon. It has been filling in nicely, but is still clearly in year 1. It has a lot of maturing to do. One thing for certain, the TTPR grew MUCH faster that the current TTTF - I sure do not miss the cutting 3-times a week I had to do last spring. I now have the annual weeds under control and my current plan is to aerate and overseed again at labor day with some more TTTF. Last summer demonstrated that TTPR in the transition zone is water dependent, which made it a high-maintenance, and generally poor chooice for the drought last summer.

Turf-type perennial ryegrass for overseeding is the way to go. If you were starting from zero I will be suggesting KBG, but since you are not, then I highly suggest PR. The turf it produces is very similar to KBG, very fine bladed dark green, and dense. It will germinate and stablish VERY quickly, and because of its agressive nature, it will suppress other grasses around it. Last year I overseeded my TTTF/Bluegrass lawn with a 3-way blend of turf-type perennial ryegrass from Turf-seed with GREAT results. PR is hardy, but doesn't have the heat tolerance of KBG. So set your expectations accordingly. Regards, Auteck