If you have Kentucky bluegrass and watered it too frequently, then thatch is a likely possibility. Otherwise, probably not.

What kind of grass do you have?
Where do you live?
How often do you water and for how long?
How often do you fertilize?
How high do you mow?

1. To be honest, I don't know what type of grass this sod is. It does not look like bluegrass; it's very green, and it grows much faster than the rest of the yard.

2. Chicagoland.

3. I watered this sod too much at first. At our Memorial Day BBQ last year there were squishy spots. That was 2 weeks or so after sod installation. I dropped down to once/day for a couple of weeks, then did about twice a week for the rest of the summer. No added water this year, but we had a very wet winter and a ton of rain in the last 2 months.

4. I put down Milorganite in the early fall. Haven't fertilized yet this year.

5. About 2 3/4".

Gonna try to add an image....

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If you are in Chicago and you have thatch, it is Kentucky Bluegrass.

I agree with auteck. It doesn't look like an extremely healthy KBG, but that's the only logical answer.

I would raise the mower 1/2 inch to 3.25 and raise it more as the temps warm up.

Here is a picture of an elite Kentucky bluegrass called Midnight. That's a small piece of wood mulch sitting on it.

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This grass is a couple years old and getting more dense year after year. The lawn is watered as needed. It is fertilized with organic fertilizer regularly during the spring and summer and gets synthetic fertilizer in the fall.

No, it is not my lawn.

Are the blades of KBG normally that wide? My grass doesn't look anywhere near that wide.

I'll try it. The problem I had last year is that if I raised the mower a notch (a Toro, 1 more notch seemed pretty high) I'd probably need to mow more than once a week. The grass grows fast and it got really high.

>"I'd probably need to mow more than once a week."

Yes, that is what we do during spring, once the grass comes out of dormancy and the growth flush begins due to the warming weather and spring rains.

Give your lawn a good raking. Pick up the dead grass / leafs and fertilize around Mother's Day. By Father's Day, all will be well.

Tall grass grows at the same rate as short grass. The apparent difference is that if you are mowing at 1 inch high and the grass grows 1/2 inch in a week, your are mowing 50% of the plant. If you mow at 4 inches and the grass grows 1/2 inch, you only mow 12.5% of the grass off. If you are following the 1/3 rule, then you would mow the shorter grass more often to avoid mowing more than 33% off at one time.

I have not grown all the varieties of KBG. The one pictured is called Midnight. The picture is very close up. The piece of wood is not a tree, it is about the size of your thumb.