To maintain good healthy grass, you need to mow it at the right height, and the right frequency. The rule that helps us figure that out is called the one-third rule, which means never remove more than one-third of the leaf tissue at any one time that you’re mowing.
So, if you’re mowing Kentucky bluegrass at two inches high, for example, you don’t want to let it grow any higher than three inches before you mow it. That does several things. It helps the clipping be small enough so that they can be dispersed across the yard, and it helps to promote the health of the plant as well.
So, the one-third rule is a guideline. There may be occasions where you’ll go on vacation, or it may be raining and you can’t mow your yard frequently enough. The grass can then get too tall. So, what do you do? You can do one of several things. You can raise your lawnmower height as high as possible. Mow it at the highest height, and then come back later that same day, or the next day with the mower deck at a lower height. Mow it again and keep the clippings on the yard, and spread them out across the yard. Or, you can collect those clippings, bag them, and take them to the nearest compost facility.
By following the one-third rule, you’re responding to how fast the grass grows. When the grass is growing very rapidly in the springtime, you’ll need to mow more often. And when the grass growth slows down in the summertime, you won’t have to mow as frequently.
It’s not necessary to bag your clippings. You can recycle them and put them back in your yard. The clippings contain nutrients and moisture, and by returning those clippings back to the yard, you’re actually recycling those nutrients and moisture back into the yard. If someone always bags their yard, that person will have to fertilize their yard more often than someone who is returning their clippings back to the yard.
By following the one-third rule, it also causes us to mow frequently enough so that it stimulates lateral growth. We want the grass to spend it’s time and energy growing across the yard rather than growing up in the air. By growing laterally across the yard, it helps the yard to be thick and dense. This helps prevent weeds and gives you a thick, healthy yard.
This feature story prepared with Rodney St.John, Kansas State University Research and Extension, Turfgrass. For more information, visit your local county extension office or visit our website at KansasGreenYards.org.