Theresa Friday
Horticulture Agent
Santa Rosa County Extension
A healthy, good-looking lawn isn’t the result of magic. It’s from using proper cultural techniques and mowing is perhaps the gardener’s most important chore. Done properly, mowing can increase the thickness of the lawn and make it more resistant to weeds. Done improperly, mowing can produce long-term damage to the turf.
Cutting height and frequency are the most critical components of proper mowing.
Turfgrass undergoes physiological stress with each mowing, particularly if too much leaf blade is removed. A rule of thumb is to never remove more than the top 1/3 of the foliage in any one cut. When the turf grows back out about 50 percent, then it’s time to mow –even if it’s not yet Saturday morning.
Recommended mowing heights for St. Augustine are 2 ½ to 4 inches. However, only the dwarf varieties of St. Augustine, such as ‘Seville,’ ‘Jade,’ ‘Palmetto,’ and ‘Delmar’ should be mowed at less than 3 inches. Centipede is best cut 2 to 3 inches.
A sharp mower blade produces a cleaner cut with less stress on the grass. Sharpening a common rotary mower blade is not a big problem and should be done often.
Rotary sharpening stones that fit on a hand drill are available. They can sharpen a blade or ‘bring out the edge’ without removing the blade from the mower housing. These, however, will just do light-duty sharpening and will not allow for balancing the blade to reduce vibration.
The best way to sharpen a rotary mower blade is to take off the blade and sharpen with a grinder or metal file. When grinding, use eye or face protection and watch out for your loose clothing and sparks.
Before working on the mower, always disconnect the spark plug wire. Tilt the mower body to reach the blade, and watch for leaking gas and oil. Chock the blade with a piece of wood so that it can’t spin. Remove the blade’s fastening bolt with a wrench or socket. Note the top side and bottom of the blade. Installation is the reverse procedure.
When sharpening the two cutting end surfaces, maintain the cutting surface angle at an angle of about 40 degrees. Thinner will be too knife-like and weak; it won’t hold up. Thicker angles will be blunter and will not cut as cleanly. As you sharpen, move the blade back and forth with light pressure. Avoid overheating the steel and losing the metal’s temper (hardness).
After sharpening, always check the blade’s balance using an inexpensive, cone balancer. A nail in a wall or stud can do in a pinch. If the blade leans more to one end, take more metal off of that end’s cutting surface to balance it. A balanced blade will vibrate less and cause less engine wear.
Never try to straighten a badly bent blade. Never try to use a cracked blade. If the blade is damaged or the cutting surfaces worn too thin, replace the blade.
Choose the correct blade type and length for the mower housing and type of mowing you do. Mulching blades have more bends and greater cutting surface than do standard blades. Mulching blades are designed to circulate the clippings and cut them several times. On most lawns, grass clippings should be returned to help recycle nutrients to the soil.
After sharpening, always check the blade’s balance using an inexpensive, cone balancer. A nail in a wall or stud can do in a pinch.