Most lawns around Lawrence are tall fescue, sometimes mixed with Kentucky bluegrass, with Bermuda and zoysia showing up in sunnier yards. The cool-season grasses do best when they're cut higher than most people expect.
For tall fescue, about 3 to 4 inches is a good target for most of the year. Taller grass shades the soil, holds moisture longer through July and August, and crowds out crabgrass, which needs sunlight on bare soil to sprout.
The one-third rule matters more than the exact number: never take off more than a third of the blade in one cut. Scalping a lawn that got away from you stresses the grass and opens the door to weeds and brown patches. If it has grown tall, bring it down over two or three mowings.
Sharp blades make a real difference. A dull blade tears the tips instead of cutting them, leaving ragged ends that brown out and lose water faster. You can see it up close: a clean cut is square, a torn one is frayed and white.
In the heat of summer, raise the deck a notch and skip mowing during drought stress. In fall, when growth picks up again, keep mowing on schedule until the grass stops growing, then finish with a slightly lower final cut so it doesn't mat down under snow.