Don’t raise the mowing height during drought

Typical advice in the paper and TV is to raise the mowing height during drought to help the turf area stay green. However, this is very simplified advice which needs clarification. Here are some well-researched facts:

• • The higher you mow a grass plant, the deeper the roots. 
• • Deeper roots mean a larger reservoir from which to draw water. 
  • Almost all turfgrass root growth is now over until this fall as cool-season grasses grow most of their roots in April-May and October-November.

Therefore, simply setting your mower up a notch or two now is not going to magically force your roots deeper because they are not growing now. Actually you will force more water stress on the plant because it will have to support more leaf material with the same amount of roots. This is a very bad decision and should not be done on non-irrigated or droughty sites. Conversely, if ample water is available throughout the summer, raising the mowing height slightly will increase the photosynthetic area of the turfgrass plant, thus allowing it to produce more energy to better survive the hot conditions. So raising the mowing height on an irrigated turf is not a bad idea. My most common advice is to mow the turf areas as high as can be tolerated for your given situation, and stick with that height season-long.

Recommended mowing heights for turfgrass species under various uses.