Proper mowing height is important in maintaining the health and overall appearance of turf grasses. Each kind of turf grass has its own recommended range of upper and lower mowing height.
Mowing near the lower end of the range in some species can be beneficial by causing an increase in the growth of the stolons and rhizomes, resulting in increased turf density. However, mowing too low will reduce the amount of leaf area which will decrease photosynthesis. This will decrease the root mass resulting in a reduced tolerance to foot traffic and to heat and water stress, resulting in a brown lawn. Mowing near the lower end of the recommended range is tolerated better during the summer months in Hawaii when our warm season grasses are at their highest growth rate. Home lawns should not be cut lower than ½ inch, very low mowing at ¼ inch or below should be restricted to golf greens and tee boxes, where turf species adapted to low mowing and special professional care and equipment is required.
Raise the height a little during the winter months when the growth rate is much slower. Even a small increase in height can produce significant benefits by allowing more leaf area resulting in deeper roots and higher stress resistance. However, mowing above the upper end of the range often results in a loose tufty appearance and a rapid growth of the thatch. This gives the lawn a spongy feel, which will lead to scalping during mowing and other problems.
The actual mowing height you use should depend on the mowing height tolerance of your particular type of grass, how often you mow, and its location. In shaded areas, for example, raise the mowing height by 30 to 50 % to compensate for the lower rate of photosynthesis of the leaf blades under low light.
A second consideration is selection of mower. The mowing tolerance of your individual turf species will be the main factor in determining the type of mower to use. The two basic types of power mowers are the reel and rotary mowers.
A reel mower is best to use on lawns cut at one inch or less. A reel mower cuts with a shearing action as multiple blades (7 to 11) turn against a stationary bed knife. The reel mower produces a better lawn appearance when the blades are kept sharp and aligned with the bed knife. Reel mowers have disadvantages in that they are more expensive to purchase, more difficult to maintain in good working condition, not very maneuverable around corners and in tight places and on uneven terrain. They do best on relatively open level lawns cut at less than one inch.
Rotary mowers should be used on lawns cut at one inch or higher. A well-designed rotary mower lifts the grass by creating suction and gives a uniform crew cut type look. A mulching rotary mower keeps the clippings in suspension long enough to re-cut them several times and discharge them directly down into the thatch. The blade must be kept sharp. As the rotary blade becomes dull it tends to produce a frayed leaf edge that dries out, giving a brown or yellow cast to the lawn. Rotary mowers are less expensive than reel mowers and are far more versatile. They handle weeds and thick grass with ease and are much more maneuverable. They can also be used to mulch and bag leaves and other small yard debris as a substitute for raking.
Mow often enough so that you do not remove more than 1/3 of the leaf growth at a time, the lower the cutting height the more often you will mow. If you follow the recommended mowing frequency, clippings should not cause a problem and should be left on the lawn. This will recycle much of the nutrients that would otherwise be lost if clippings are bagged. As much as 50% of the nitrogen fertilizer you put onto the lawn can be retained in this manner.
Table of Mowing Information
|Turf Species||Recommended Mowing Height (inches)||Preferred Mower||Approximate frequency (inches)|
|Common bermudagrass||1 to 2||rotary||7|
|Improved common bermudagrass||¾ to 1 ½||reel/rotary||7|
|Hybrid bermudagrass||½ to ¾||reel||5 to 7|
|Seashore & other varieties of paspalum||½ to ¾||reel||5 to 7|
|Emerald zoysia||½ to ¾||reel||7|
|Z3 & newer varieties of semi dwarf Zoysia||5/8 to 1||reel||7|
|El Toro zoysia||3/4 to 1 1/2||reel/rotary||7|
|Centipedegrass||1 ¼ to 2||rotary||7 to 14|
|St Augustingrass||2 to 3 ½||rotary||7 to 14|
Jay Deputy is the state administrator for the Certified Landscape Technician program and a member of the LICH Board of Directors.