Lawn Mowing 101 No single mowing height is correct for all lawn grasses - all have different growing habits, fertilizer and water requirements. What we do know is that close mowing reduces root growth, thus reducing the amount of water the turf can absorb. Shallow roots are susceptible to hot weather and water evaporation, and need more water to keep the grass alive. During the hot, dry days of summer, it's good policy to let your grass grow just a little bit longer, so raise the mower height a little more than usual and your lawn will be better able to survive those summer scorchers - and of course it will look a lot better as a result. Lesson 1: Mow lightly and frequently, following the rule of one third -- never cut off more than one third of the grass blade at any one time. To cut off more than one third stresses the grass too much. Lesson 2: Adjust your mowing schedule to take into account different growth rate periods. In the spring, your lawn may grow two inches per week, but only one inch during the summer. Mow more frequently during the period of fastest growth, and less frequently during the period of slower growth. Lesson 3: Adjust your cut (or mowing height) during periods of stress like drought or heat. Allowing the grass to maintain a larger blade area will shade the roots, and reduce water evaporation from the soil. In shady areas, mow the grass higher as well, so that there is more blade surface area to catch the needed sunlight. Lesson 4: Vary your route or cutting path each time you mow your lawn. Running the mower in the exact same route week after week creates ruts in the lawn and compacts the soil under the wheel tracks. Alternate directions each week, and be sure to avoid overlapping as much as possible to create uniform stripes. Lesson 5: Keep your mower blades sharp! When mowing blades are dull, they smash and pummel the grass blades rather than cutting them. The resulting ragged ends will turn brown and make the lawn look shabby. A rough cut will also make the grass more disease-prone. Residential homeowners should sharpen their blades at least twice a season. Commercial cutters should sharpen their blades at least weekly.