Ah, geez folks. Chances are that this one is a classic, textbook example. The OP gave you everything except the answer. DJS: Please answer the following detail questions: (1) does the lime-green grass have a tendency to seem to like a bit of shade? (2) what did the areas that were in full-sun do during the hottest parts of the Summer? What did they do when the weather began to cool a little? (3) does the lime-green grass tend to "lay-down" somewhat when it is mowed more than 2" tall? (4) go out onto the lawn and gently lift the lime-green grass. Do you find that it is not straight into the soil, but runs horizontally along the soil? If it does, what color are the stems below the grass? (5) Are the backs of the grass leaves shiny or dull? (6) How big are the patches of lime-green? Are they roughly circular? Do they spread outward and grow larger? (7) Does it seem to like the moist areas?

When did you last use the weed killer? Check the label to see how long you need to wait after using it before seeding. TTTF doesn't usually spread to fill in, although it can spread a little through tillering (where a new plant crops up right next to the existing plant). Whether bluegrass will be a good idea depends on where you are. Zone 7 doesn't really tell us enough to know whether it will work there. Some parts of zone 7 get too hot for KBG to thrive. If that's the case you can periodically overseed with TTTF. There are some newer varieties of TTTF that will spread via rhizomes, so you could try incorporating some of those if KBG won't work.

Clare, which does best for you might depend on where you live - have you checked around for what's thriving in your own area? Most of them have their origins in the Mediterranean, sun, sandy quick draining soil that is neutral to alkaline in ph, dry winters. My own garden couldn't be more opposite, acidic soil, clay based, long wet winters - Grosso (Lavandula x intermedia 'Grosso') has worked out better than munstead, hidcote lavenders for me here. Any I plant just about have to be sited on sloping ground.

You need a fine bladed dark fescue. Check NTEP tests for your area, they rate both attributes. Rhambler should fit the bill.