Where do you live?
What kind of grass is that?
When were the last two times you fertilized and what did you use?
What is your watering regimen (frequency and duration)?

1) Grosse Ile, Michigan (Zone 5B)
2) Midwest Mix - Mostly PRG
3) This year I've put down Milorganite at bag rate twice... about 30 and 60 days ago. Also put down a broadleaf preventer about 45 days ago that had a small amount of nitrogen in it.
4) Water almost every day (free water)... 7 zones... 15 minutes per zone (each zone = 5 Rain Bird AG5 impact heads)... never measured how much water that actually equates to in inches. I've tried watering deeper and less frequently, but that didn't seem to work very well.

This post was edited by bajafx4 on Mon, Jun 17, 13 at 1:34

I would like to see you have the blade sharpened. Then cut the grass parallel to the water. Set your cut to your closes setting to 3 inches.
Cut grass this week and then next and show me the pictures.

I can cut the lawn parallel to the water, but the mower blades aren't a problem. I purchased brand new blades two weeks ago (Oregon GatorMulcher G6) and even put a slightly sharper edge on them right out of the box. I've only cut with them three times.

Also, the lawn needs to be cut more than once a week. I cut it about every 5 days and even that is pushing the limit of how much I should be cutting off. It's extremely thick and fast growing... just not super dark green.

Here's my take (whether it's right or wrong that's for you to decide). If you mow at 4", it's probably 5-6 inches tall when you cut it. Grass that tall, especially perennial rye, has a longer stalk/sheath than grass that's kept at say 2.5-3 inches. When you cut away 1-2" of grass blade, you are removing the greenest part of the lawn, and revealing more of the sheath, which is generally much lighter. Now when you mowed that path at 2.75, you effectively removed most of the grass blades and some sheath, leaving you with just sheaths, which is why it was brown for a few days after mowing. You also shortened the sheaths compared to the rest of the lawn. The change was the new blades emerging from the newly shortened sheaths. So now the path area has grass with more blade relative to sheath than the rest of the lawn, which is why it's darker green. I suspect that if you mow the whole yard at just 4 inches the darker green path will fade as the grass reverts back to it's longer sheath length.

This post was edited by tiemco on Tue, Jun 18, 13 at 13:29

Ahhh. The wisdom of tiemco. I agree.

You might want to experiment with lowering your blade.

Sorry, no close up pictures... rain all evening yesterday.

Timeco - That makes sense, but at the same time it seems to go against the general conception that longer grass = deeper/darker green. Is it because I have mostly PRG and maybe I should mow shorter than 4 inches?

Sorry dchall... didn't see your post. I'm going to try lowering the deck on half the lawn and see what happens.