There are few hard and fast rules for lawn mowing. Different grasses flourish at different times of year, experiencing seasonal growth spurts in response to either warm or cold weather. During periods of rapid growth, grass should be cut routinely, regardless of the outdoor temperature. In other words, grass should be mowed when it needs it, not according to a schedule, thermometer or calendar.
As the name implies, cool-season grasses grow best in cold climates. Popular throughout the North, they flourish in the spring and fall, where they often remain green beneath the winter snow. That being said, do not mow these grasses when they are covered in snow or frost; wait for the ice to melt before trimming the blades to avoid damaging the fragile plant tissues. Cool-season grasses also have a tendency to turn brown during periods of hot, dry weather. Do not mow the lawn in the summer until the grass turns green and begins to grow again. Allow the lawn to reach at least 4 inches in height before trimming as this will help protect the roots from burning.
Warm-season grasses thrive in hot climates. Common throughout the South, warm-season grasses grow most actively during the sultry days of summer, displaying a rich green color even when exposed to high heat, endless sun and periodic drought. Accordingly, they go dormant during periods of cold weather and generally do not need to be mowed once the daily high temperature drops below 50 degrees Fahrenheit.
Native grasses, such as buffalo grass, prairie grass and blue grama grass, create tough, drought-tolerant lawns that prosper under difficult conditions. Some native grasses grow so gradually they never need to be mowed at all; others may require a periodic trim -- one in the early summer and another in early fall. These slow growers may take a few weeks to germinate, but once they are established, native grass lawns are virtually maintenance free needing no irrigation or fertilization. They are also tolerant of extreme temperatures and can withstand summer highs of up to 120 degrees Fahrenheit and winter lows down to negative 40 degrees.
Regardless of grass type, set the blade on the mower so that it removes no more than 1/3 of the current growth. Cutting the grass too short stresses the plants and weakens the root system, resulting in thin, weedy lawns. Sharpen the mowing blade at least once a month during mowing season. A dull blade tears the grass, rather than cutting it cleanly, causing the lawn to look ragged and shaggy. During periods of rainy weather, wait for the grass to dry before mowing since damp grass clings to the mower blades and soft, wet soil is easily damaged by heavy equipment.