Mowing Height Effects:
As can be seen, the lower the lawn is mown, the paler the remaining grass appears. Recovery time to green-up takes longer. And, the lawn is stressed because the amount of photosynthetic area is reduced. Rooting depth is reduced because less nutrients are being produced by the grass plants. Mowing high (3 ") and more is recommended!
Thatch Depth Effects:
Thatch layers are made up of living and dead root fibers and crowns of grass plants. Clippings lay on the top and are easily decomposed. Clippings add little to the thatch layer. Collecting clippings when mowing reduces nutrients availability by much as 1 pound of Nitrogen per year, which should be replaced. One half (½") inch or less thatch holds moisture in the soil, allows oxygen into the root zone and cushions the crowns of the plants. More than ½ " of thatch has the opposite effect. Plus, thick thatch acts as a harborage for insects and diseases. Annual aeration is highly recommended when the thatch layer is greater than ½".