Hello - my husband and I are first-time home buyers/renovators. The house came with a weedy awful backyard. This past june, we paid a landscaper to remove the debris, river rock, old weed cloth, garbage, weeds and rats (!) from the yard, grade it, and put in 3" of new topsoil. Then we laid sod ourselves. We bought the sod from a highly-recommended sod vendor, and spread a thin layer of commercial lawn fertilizer (according to package instructions) on the new topsoil prior to putting down the sod.
It went in easily, we watered regularly for a week, then tapered off the watering over the next 2 weeks. The lawn took off. Within a couple of weeks you couldn't see the edges of the sod and the lawn was lush and deep and we were so pleased!
Then, we got busy with house renovations and a toddler and life, and forgot to mow it for, umm, like 3 or 4 weeks. In the height of an Illinois summer and it was growing like mad and got very deep.
My husband mowed it (with a cheap push mower, as it's a very very small yard) and we noticed that underneath the long deep green grass there was a lot of dead grass. Then we did that again (I know, I know). Another 3 or so weeks, it got deep, we mowed again and suddenly our lush green lawn looks TERRIBLE. Below the thin blades of green grass, there's a thick thatch of brown dead grass that comes up loosly if you tug at it.
While we haven't been watering, that's been by choice because it's been raining fairly regularly, and mushrooms pop up pretty often so I do not think that it ever got too dry. It always feels damp if I put a finger down into the roots and soil.
Help! what did we do to our beautiful lawn? Did we kill the roots by letting the blades get too long?
I read that when a lawn is stressed that's NOT the right time to fertilize, so I haven't done that.
Any suggestions, besides do what we know we were supposed to all along and mow weekly, taking less than 1/3 of the depth of the grass at a time?
Here's an image: