What Is The Correct Mowing Height For My Lawn?

This is a question many homeowners have asked. The reason it is asked is simple; the lower one mows their lawn, the less the have to mow it and the sharper it will look, right? Well, not exactly.

The 1/3 Rule

The general rule about how much of your grass can be cut if with each mowing is about 1/3 of the leaf blade. Removing more than 1/3 of the leaf blade at a time can send the plants into shock which will cause your lawn to weaken. The plant needs enough green space to create energy from the sun the same way our bodies need enough food to allow us to function.

The larger issue, however, is that the shorter the lawn, the less healthy it will be. The shorter the grass blade is, the less the lower part of the blade and the root system will be shaded. This means that the plant will lose a lot of water thtough transpiration and evaporation. In the summer, this can have a devastating effect on your lawn. It will essentially dry out.

Fewer Weeds

Your lawn will also have a lot more weeds. Consider this; the longer the grass blade is, the less room there is for weeds to grow. Conversely, the shorter the grass blades, the more room there is for weeds to grow and, eventually, dominate the lawn. It is a simple matter of competition for space.

We recently visited the University of Maryland Turfgrass Research Facility in College Park, Maryland. It is a lawn nerd’s heaven! There, we observed the four test plots pictured below showing the effects of mowing grass at 1”, 2”, 3” and 4” heights. Each plot was fertilized the same, similar to how we fertilize our client’s lawns. The test plots received no weed control applications.

Notice how poor the 1” and 2” lawns look. They are thin, off color and full of weeds. Conversely, the 3” and 4” lawns are thick, have better color and fewer weeds. The difference is strikingly clear.

From these test plots it is clear that mowing lawns short does not result in a nice looking lawn. In fact, just the opposite, an under colored, patchy lawn with weeds, at best. At the same time, we can understand why homeowners would not want their lawn mowed at 4” as it can become sloppy looking quickly. Our best recommendation is to set mowers at 3”.  At this height, a lawn still looks neat and crisp and has the benefit of being able to crowd out weeds.

 

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