Following proper guidelines for mowing, fertilization and irrigation will help keep thatch accumulation to a minimum. Mow at the proper mowing heights and follow the 1/3 rule to keep the grass from becoming stressed. Fertilization to avoid excessive growth also is important in preventing thatch buildup. Never apply more than 1 lb of nitrogen per 1000 ft² at any one time, especially in the spring when the grass is growing vigorously. Irrigate to encourage deep rooting will also keep thatch to a minimum. Remember to water ‘deep and infrequent’ for best results.
The simple, everyday task of mowing your yard is commonly overlooked in terms of its importance to the overall health of the lawn. If done correctly, mowing will not only make a lawn look nice, but will keep it healthy and more resistant to stress and invasion from weeds, insects and diseases.
Although there are differences in optimal mowing heights among different types of grasses, for most home lawn situations, a mowing height of 3 inches is a good target. Some grasses can tolerate lower mowing heights, such as perennial ryegrass and Kentucky bluegrass, but mowing too low decrease root growth and makes the lawn more susceptible to drought and heat stress as well as increases the incidence of weeds and diseases. Never mow your lawn lower than 2 inches.
Some people recommend lowering the mowing height in the spring and again in the fall, but this is not absolutely necessary. It is more important to maintain the proper mowing height and to mow frequently. Continue mowing late into the fall until the grass has stopped growing, sometimes as late as late November. This will remove excess debris and decrease the chance of snow mold. Raising the mowing height in the summer is a good practice. This higher mowing height, encourages deeper root growth and increases the lawn’s resistance to drought stress. Even a 1/4 inch adjustment (one wheel notch on most rotary mowers) will make a big difference in the health of the grass.
Check your owner’s manual for the correct height setting or place the mower on a flat surface and use a short ruler to check the distance between the mower blade and the ground. BE SURE MOWER IS OFF AND DISCONNECT THE SPARK PLUG WHEN MAKING ANY ADJUSTMENTS AND WHEN CHECKING BLADE HEIGHT.
The rule to use for determining how often to mow is the 1/3 rule which states: Never remove more than 1/3 of the leaf blade height at any one mowing. So, if your mower is set at 3 inches, you should mow when your grass reaches 4.5 inches. Violating this rule not only scalps the grass and makes it look unsightly, but also puts the grass under stress. If you just can’t seem to keep up with the growth of the grass, try raising the height a notch and slowly lowering the mowing height over time to get back at the desired height.
Contrary to popular belief, grass clippings are not a major contributor to thatch. Grass clippings are composed primarily of water and breakdown fairly rapidly in the soil. As long as you are following the 1/3-rule, the clippings will not accumulate on the lawn and should filter back into the lawn. If you are not mowing frequently enough, large clumps of clippings on the surface should be removed because they will decompose slowly and may smother the grass. A hint in dealing with excess clippings is to let the clumps of grass dry for an hour or two and mow them again. This will help break up the clippings into smaller pieces and distribute them more evenly over the lawn.
For additional information on grass clippings and their management see the University of Idaho’s publication: Don’t Bag It!
Rotary mowers are the most common mower for homeowners. It is important to keep the mower blade sharp so the grass blades are cut cleanly. Too often this is overlooked causing the blades to tear and rip instead of being smoothly cut off. Ripping leaves blades open to diseases and stunts the grass. Sharpen the mower blade approximately every 4-6 weeks depending on the size of your lawn. If sharpening the blade yourself, use a file and follow the original bevel of the cutting edge, moving the file towards the cutting edge. Test the blade for balance by placing a screwdriver through the center hole checking to be sure the blade remains horizontal. If not, you may need to remove metal from the non-cutting edge of heavier side until balance is reached.
Reel mowers are not as common and cut grass blades with a scissors-type action. These types of mowers are much more difficult to sharpen at home. Additionally, it is important that the stationary bedknife be properly adjusted to the cutting reel for a proper cut. Check with a hardware store or lawn mower mechanic for proper adjustment and sharpening of reel mowers.