Sounds like poa annua that dies when heat and hotter weather arrives. Do a search on this forum about how to try to deal with it (very tenacious).

Wow! I'm glad this came back around. I think everyone has learned something since this thread was started. And now Houzz does notify you when messages you have posted on get more action. So maybe we can tune both of you up at the same time. You should not have to core aerate, ever, with very few exceptions. If you have hard soil there are chemistry reasons and biological reasons for that. The chemistry reason is most often an imbalance in the salts (magnesium, calcium, sodium, and potassium). Those can be addressed with a good soil test. The better lawn forums have been recommending Logan Labs in Ohio for soil testing for the past few years. Their $25 test is what you need. They will email the results to you. If you post them here morpheuspa will give you an extensive reading of the results and get you on your way toward soil perfection. The other reason the soil might be hard and clay-like is biological. There are fungi in the soil that will soften the soil for you once they have been well fed and watered. Spraying the yard with a surfactant will go a long way to allowing water to penetrate the soil and create the environment needed for healthy beneficial fungi. The surfactant can be anything but some are better than others. Ordinary shampoo is a good one. Any clear shampoo, like baby shampoo, will work. Spray the yard at a rate of 3 ounces of shampoo per 1,000 square feet and follow that up with 1/2 inch to 1 inch of water. Allow it 3 weeks to work. If you have other reasons for core aeration, please, lets discuss them. You should also not have to treat for insects unless you have found them in sufficient numbers to treat. The first clue you might have a grub problem is when you see beetles swarming your porch lights in May and June. If you see that then in July, before you see any damage, dig up a square foot of turf down to about 2 inches looking for grubs. If you see fewer than a dozen, then you don't have a grub problem. If you see an uncountable mass of them, then spray. Chinch bugs are more of a southern problem because they like hot soil, but it is possible to see them elsewhere. Spraying insecticide as a preventive measure is not good for the soil biology. Insects are an integral element of healthy soil. Spraying insecticide kills off the bad bugs, but if you don't have bad bugs, then it just kills the beneficial insects. I suspect both of you have watering and mowing height issues. Here's something I wrote a while ago that summarizes what I've learned over the past decade or so. Basics of Lawn Care After reading numerous books and magazines on lawn care, caring for lawns at seven houses in my life, and reading numerous forums where real people write in to discuss their successes and failures, I have decided to side with the real people and dispense with the book and magazine authors. I don't know what star their planet rotates around but it's not mine. With that in mind, here is the collected wisdom of the Internet savvy homeowners and lawn care professionals summarized in a few words. If you follow the advice here you will have conquered at least 50% of all lawn problems. Once you have these three elements mastered, then you can worry about weeds (if you have any), dog spots, and striping your lawn. But if you are not doing these three things, they will be the first three things suggested for you to correct. 1. Watering Water deeply and infrequently. Deeply means at least an inch in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. Do not spread this out and water for 10 minutes every day. If your grass looks dry before the month/week is up, water longer next time. If that does not work, then you might have to water more than once per week during the summer's hottest period. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds. You will have to learn to judge when to water your own lawn. If you live in El Paso your watering will be different than if you live in Vermont. Adjust your watering to your type of grass, temperature, humidity, wind, and soil type. It is worth noting that this technique is used successfully by professionals in Phoenix, so...just sayin.' The other factors make a difference. If you normally water 1 inch per week and you get 1/2 inch of rain, then adjust and water only 1/2 inch that week. 2. Mowing Every week mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. However, bermuda, centipede, and bent grasses will become the most dense when they are mowed at the lowest setting on your mower. In fact there are special mowers that can mow these grasses down to 1/16 inch. Dense grass shades out weeds, keeps the soil cooler, and uses less water than thin grass. Tall grass can feed the deep roots you developed in #1 above. Tall grass does not grow faster than short grass nor does it look shaggy sooner. Once all your grass is at the same height, tall grass just looks plush. 3. Fertilizing Fertilize regularly. I fertilize 5 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above. Follow the directions on the bag and do not overdo it (unless you use organics in which case you may overdo it without fear of hurting anything). At this point you do not have to worry about weed and feed products - remember at this point you are just trying to grow grass, not perfect it. Besides once you are doing these three things correctly, your weed problems should go away without herbicide.

"mixed in with some green" "On the other side of my driveway, the strip of lawn that was most decimated by the grubs and reseeded last fall & this spring looks great." I bet you have grubs again. The inconsistency of the problem leads me to beleive that grubs are responsible for the damage. They like sunny, well watered locations near concrete (ie curbs, sidewalks, driveway) Do a grub test, pick up the soil and look under it for grubs. If you had grubs before (you mentioned it) then you probably have them this year too. Get some Milky Spore or some Bayer 24hrs Grub killer. Forget the ones that offer "control" or "season long" or "good for three months" you're past that point if you have grubs present in your soil/turf. The only other disease that resembles grub damage is Phytium Blight. Dog urine can some times have similar effects. I hope it helps.

Where in the world are you? Do you live where there are watering restrictions? Now is the time to take a good look at the soil and make any corrections that will help make that soil into a good healthy place to grow plants. A good reliable soil test will be a start so you know what the soil pH and major nutrient levels are and these simple soil tests may be of some use as well. 1) Soil test for organic material. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top. 2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains’ too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up. 3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart. 4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell, to a point. Too much organic matter can be bad as well. 5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy. kimmq is klimmsr