Poa grass should be re-named devil grass. My entire back yard is all poa.Two years ago, it was maybe 25%. We Dug, Pulled, Used round up when the bermuda was dormant, and have tried everything. This year it is impossible. It has been too cold here in Jackson,tn. to make this stuff die. We have just given up. When you are spending so much on your lawn and this stuff just grows and grows it is a big waste of money. Is there any thing that will eliminate this stuff? and where did it come from?

I can't answer when they germinated. You do want to put down a pre-emergent in the fall and spring. I'm not sure of the temperature. I would Google to see at what temp it germinates or someone else will answer. The one thing I am sure of is dimension works. I had a huge poa problem the last few years to the point I was thinking about using a lawn company and I have ALWAYS been a dyi person. I used dimension from Lesco and I had no poa at all this year. You can get it from a John Deere store or home depot carries pre-m which is supposed to stop poa. Good luck and hang in there. I know it is extremely frustrating.

Where do you live? Your USDA zone and Sunset zones have more to do with selecting plants than how to grow them. Your location will help with soil issues, too. I'm pretty sure you don't live at Big Bear, but there are a lot of soil types just coming out of the 90s. When you say TF, do you mean Marathon? Because it can be misleading. Marathon is a TF but it is a dwarf variety. In most places Marathon is a horrible water hog and should be replaced with something like Bermuda or St Augustine. Need to know what you live.

I'm no help with the poa issue. As far south as I am it is not much of an issue. I see it in the lawn, but only for a few weeks (long enough to go to seed, though). Overseeding KBG? Why? Especially when it's as dense as yours seems to be? I think you're watering too frequently...unless your temps are running over 110 degrees F. Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall. There's a very small chance you have clay. Are there brick factories nearby? If not you probably don't have clay. It is much more likely you have a soil with an imbalance of salts like calcium, magnesium, sodium, and potassium. That can be corrected once you have a good soil test (Logan Labs $25 is the test you need). You can see for yourself whether you have clay by doing a jar test. Find a clear container, fill it half way with soil, fill it the rest of the way with water and a few drops of soap. Measure up the side with a ruler and take a picture to see how many inches of soil you have. Then screw the top on the jar and shake it like crazy. Set the jar down with the ruler next to it. At 2 minutes take another picture. At 2 hours take another picture. At 2 days take another picture. The material that has settled after 2 minutes is sand and gravel. After 2 hours you'll get the loam. At that point if you can see through the water on top so that you could read something held on the other side of the jar, then you have zero clay. Everything that will settle will settle by 2 days. Suspended clay particles will still cloud the water after 2 days. Then you can use the measurements of settled material in your pictures to determine the proportional content of your soil (sand versus loam versus clay). Zones are only used to select plants for winter hardiness. Once you pick a plant, then the zone is meaningless for care. For example I think Oregon has most of the zones except 9 and 10. But I would not think to grow bermuda there.