The first step in good mowing is to have a sharp blade. If the blade has not been sharpened in the past year, it needs to be sharpened or replaced. Dull blades whip the grass ends rather than cutting the grass. The ragged ends left by a dull blade cause a lawn to look yellowish the day after you mow. Ragged grass blades also lead to more water use by the grass and possibly an increase in disease.
Zoysiagrass lawns need to be cut at a height of 1 to 1 1/2 inches. Rotary mowers can do a good job if your lawn is relatively smooth and you keep the blade sharp. Otherwise, a more expensive reel mower will be needed. It is best to start at a 1 inch height in spring and gradually raise the height when hot weather arrives. Research indicates that a height of 2 inches is best when growing zoysia in partial shade.
Measure the mowing height by stationing the mower on a flat surface and noting the distance between the blade and the ground. Make sure all four mower wheels are set to the same height.
The grass will need to be mowed whenever it has grown to 3 inches tall. In this way, only one third of the green part of the plant will be removed by mowing. If you allow the grass to get much taller than 3 inches you’ll mow down into the stems that have grown tall and the lawn will not look its best after you mow. Zoysiagrass is a slow-growing grass and it can fool you with its mowing needs. Mow it regularly to avoid a build-up of thatch under the turf.
In fall, let the grass go dormant without excessive mowing. It will have a nice brown color during the winter. In mid March, mow off the top brown blades to expose the soil to the sun and warm the soil. Scalping the grass very low is not necessary. Burning the dead grass is also not recommended. It is illegal in most areas and it is dangerous in all places.
It is not necessary to catch the clippings when you mow. Research has shown that letting the clippings fall on the ground does not lead to disease or thatch problems. The clippings actually return nitrogen to the soil and save you money on fertilizer.
Zoysiagrass does not usually form a thatch layer under the grass if it is mowed regularly. Using a de-thatcher when it is not needed can hurt the grass more than it helps. If the turf seems to be growing directly in the soil and if the thatch is less than 1/2 inch thick, don’t use a dethatcher. If you have thatch, the best way to remove it is to topdress the turf with a 1/4 inch layer of clean topsoil. The microorganisms in the topsoil decompose the thatch without the need of a mechanical dethatcher. Chemicals which claim to remove thatch when they are sprayed on the lawn have not been proven effective.
Q: I’m having a hard time pushing my mower through my zoysia lawn. Can I thin it out somehow?
A: I suspect you have been mowing the grass too high. Zoysia should be mowed no higher that 2 inches tall and preferably 1 and 1/2 inch tall. After the zoysia has fully greened next spring, rent a power dethatcher. One trip over your lawn may be adequate to thin it or you may need to make another pass at right angles to the first. The machine will throw up great mounds of grass and thatch: rake it up and put everything on the compost pile. Fertilize the lawn lightly and water thoroughly to stimulate the grass to grow back rapidly.