It's a pity to break your weekly routine, but if your grass is growing, you need to be mowing. Each grass type looks best and stays healthiest at a certain height. Letting the grass grow too long can be just as damaging as giving your lawn a too-short crew cut. Avoid cutting more than one-third of the leaf blade. If these guidelines work out to your mowing every Saturday, fine; however, weather and growth spurts may require adjusting your schedule. Scalping the lawn is a common mistake. In the cooler spring and autumn weather, cut grasses shorter. When temperatures start topping 80 degrees F, let the grass get taller. It won't have the same 'perfect' appearance as a lawn cut shorter, but plant health will more than make up for style. Taller blades shade the ground, conserving moisture and preventing weed seeds from germinating.