Believe it or not, proper mowing is the single most important factor in maintaining the health of your lawn – outweighing even irrigation and fertilization! Good mowing practices affect the density, texture, color, disease and pest resistance, and overall health of your lawn.
So… what’s so special about the 1/3 rule?
Mowing removes the uppermost, green shoot growth of your grass. This is where photosynthesis takes place. If you cut off more than 1/3 of the shoot height, the rate of photosynthesis drops significantly. The remaining growing portions of your grass will be “hungry” for sugars. Since shoots take priority over roots, sugars will be diverted from the roots to feed the shoots – creating a weaker and shallower root system.
Shallower roots and fewer available sugars also mean your grass will have a harder time coping with environmental stresses like heat or drought. You may have to water more often to keep your grass from drying out.
Blades of grass grow from the bottom – from a point called the crown, located a few centimeters above the soil surface. Removing more than 1/3 of your lawn’s shoot length in a single mowing removes the natural cushioning that protects the crown from drying out and from physical injury. Your lawn may turn brown and become patchy and thin if the crowns are damaged.
Cutting your lawn extremely short can put the crowns under so much stress that the lawn actually dies.
When your lawn grows longer than usual, maybe from excessive rain or because you were away on vacation, you should still abide by the 1/3 rule. Adjust your mower height so only the top third of the lawn will be removed. Wait several days, adjust your mower height again to remove another 1/3 of the blade height. Continue like this until your lawn is back to the height you prefer.
It may take several weeks to get your lawn back in shape, but this gradual process is far healthier for your lawn than aggressive mowing.
If you’ve just installed new sod, you must wait until the roots have established before mowing. This can take between two and four weeks, depending on the season and weather conditions.
Looking for more mowing tips? Find more here.