MOWING HEIGHT MATTERS: Recommended Height of Cut
Pam Newcombe

PJC Organic loves the moniker “Mow High – May, June, and July”. We often discuss the value of cultural practices and how mowing can make or break a program. Last week’s blog covered 7 recommendations for proper mowing. Furthermore, this week we’re going more in depth on why mowing height matters.

Shoot & Root Growth

graphic showing longer turf blade results in longer root development to show mowing height matters

There is a direct relationship between the top growth of the grass and the root growth of the grass. Meaning a lawn maintained at 3+ inches has a more robust root system than one maintained at 1.5 inches. Therefore, longer grass is  more drougtt tolerant and able to better withstand grub pressure.

Years ago, Michigan State University Extension School published an article titled “Raise Your Mower Height to 3.5 Inches to Help Grass Withstand Grub Damage”. In it, Bob Bricault stated:

“Studies show that turf irrigated daily in mid- to late summer can tolerate higher populations of grubs before damage occurs. Now scientists are looking to other lawn cultural practices to help reduce the use of pesticides in the battle against grubs. New research shows that raising the mowing height results in a large increase in root mass. A larger root system lessens the chance of damage by grubs that feed on these roots.

Smitley states, ‘Research at MSU indicates that if turf root systems are dense enough, it is unlikely that grubs will consume greater than 60 percent of the root mass, which will leave enough roots for your lawn to survive without seeing any dead patches.’ Setting your mower to a height of 3.5 inches above the ground will help the turf develop this larger root mass.

The combination of turf growing at 3.5 inches along with watering lawns during dry periods makes it unlikely that grubs will damage the lawn. “Cut it high” is more than a slogan; a higher mowing height helps crowd out weeds, promotes deeper roots and helps the lawn withstand drought conditions. Now another benefit can be added: it prevents grub damage without the need for insecticides.”

Benefits of Mowing High
  • Deeper root system
  • More drought tolerant with greater access to water & nutrients
  • Better able to withstand pest pressure
  • Shades soil to keep it cooler and prevent weed seed germination (particularly crab grass)
  • More stress tolerant
  • Improved photosynthesis
  • Longer time between cuts when following the 1/3 rule
Recommended Mowing Height

Slowly raise cut to 3.5 inches by mid-May. Residential lawns may be maintained at 3 – 3 ½ throughout most of the season. During extreme heat, consider maintaining a HOC of 4

how much roots, tur grass blades, temperaature, and microbial activity fluctuates based on season

Organic turf care is designed to keep toxic herbicides and pesticides off of lawns, out of waterways and keeping areas safe for families, athletes and pets. One of best ways to accomplish this is to recognize mowing height matters and MOW HIGH.