When to Mow
Most southern turfgrasses do best mowed lightly and frequently. Studies show that this stresses the grass plant less than heavy, infrequent cuttings. The general rule is cut no more than 1/3 of the grass blade at any one cutting. Otherwise the grass loses too much of its energy-storing foliage and has to rapidly replace it at the expense of root development. The stress of losing more than 1/3rd of the foliage surface makes grass plants more vulnerable to pest and disease problems.
To maintain the lawn at the recommended minimum of 2 inches, for instance, mow before it reaches 3 inches; to keep it at 1 1/2 inches, cut at a little over 2 inches. This means more frequent mowing when southern grasses are growing vigorously, but it is better for the grass.
One time that you mow the lawn very short is when cutting the grass the first time in spring. This removes the dead or damaged tips. Mow a southern grass that goes dormant in winter as soon as danger of frost in your area is past. Collect the clippings and put them in the garden as mulch or in the compost pile.
Small changes in mowing height make a big difference in a lawn’s health and vigor. Because warm season southern grasses have a reputation for tolerating closer mowing, some homeowners mistakenly mow too short. Increasing the height of your grass only 1/8 inch adds about 300 additional square feet of leaf surface for each 1,000 square feet of lawn. The extra leaf surface enhances grass growth above the ground and--even more importantly--under the soil. Conversely, shearing grass too close to the soil surface reduces the grass plant’s ability to metabolize food, inhibits root development, opens the turf to weeds, and lowers drought resistance.
Tall Grass Has Fewer Weeds. - Routinely mowing southern turfgrasses such as Bermudagrass and zoysia to a minimum height of 1½ inches reduces weeds because the longer blades block sunlight that ever-present weed seeds in the soil need to germinate.
Tall Grass Has Deeper Roots. - Allowing the grass to grow taller encourages the roots to grow deeper. Good roots give plants more staying power during drought. Tall grass shades the soil, cooling the crowns of the grass plants and reducing soil drying. Mow grass ½ to one inch higher in shady areas. This gives shaded grass more leaf surface for photosynthesis to compensate for reduced sunlight.
Mowing Height Chart
Type of Grass Minimum Height
Bahia grass 2 ½ to 3inches
Bermudagrass ½ to 1½ inches
Centipede 1 inch
Kentucky Bluegrass mix 2-3 inches
Perennial Ryegrass 2-3 inches
St. Augustine 2 ½ to 3 inches
Tall Fescue 2 to 3 inches
Zoysia 1 to 2 inches
Leave the Clippings
There are lots of reasons to leave the grass clippings on the lawn when you mow. To avoid clumping use a mulching power lawn mower or fit your standard rotary mower with a mulching blade.
Leave clippings to fertilize - When the clippings decompose on the lawn all season, they provide 25% of your lawn’s annual nitrogen requirement.
Leave clippings to mulch - Left to fall among the grass blades to the soil, grass clippings serve as a temporary mulch, blocking the evaporation of moisture from the soil.
Leave clippings to save time - It takes 30% less time to mow a lawn and mulch the clippings than it does to mow, collect and bag them.
Clippings do not cause thatch because clippings are mostly water. Thatch consists of surface roots and accumulated dead plant parts that build up on the soil and sometimes trap grass clippings temporarily. Zoysia and hybrid Bermudagrass lawns tend to build up thatch. Frequent mowing at recommended heights and removing excess clippings when you have gone too long between mowings help control thatch. “Scalping” the lawn in early spring by mowing it very short to remove accumulated dead plant debris helps too. If thatch becomes serious, remove it with a dethatcher or vertical mower available at equipment rental centers.
Mow with a sharp blade. Sharpen your mower blade at least once a season, preferably twice for best performance. A dull blade leaves frizzy ends on grass blades, which cause them to lose more water and become more vulnerable to disease.
Don't cut wet grass. It causes uneven mowing and messy clumps of clippings which may mat and block light from the grass. If there is some fungal disease in parts of the lawn you will track it over the whole lawn.
Pick up stones and sticks before mowing. Rotary mowers can “throw” debris from under the machine, causing injury.
Alternate mowing patterns. Mowing in the same direction every time tends to compact the soil and causes wear patterns in the turf.
Topdress with your last mowing. Mow right over the last 1/2 inch or so of fallen leaves to provide organic matter for the soil. They will decompose among the grass blades over the winter, adding organic material to the soil.