What is the One-Third Rule?

What is the One-Third Rule?

Whether you’re scrolling through lawn forums or YouTube videos, one comment, post or mention that is sure to pop-up is the one-third rule for lawn mowing. It’s a simple principle where you are mowing the grass at the right height and proper frequency.

This basic turf management rule applies for golf courses and home lawns. Keeping your turf properly cut can help keep it healthy, less stressed, and promote a thicker turf.

What is the 1/3 Lawn Mowing Rule?

The one-third rule means to never cut more than 1/3 of the grass blade at a time in a single mowing. Example, if you keep Turf Type Tall Fescue at 4′”, mow the grass before it exceeds 6″ (1/3 of 6 is 2 – cut 2″ or less each mowing). Another example is if you keep a low 2″ cut on Kentucky Bluegrass, cut the turf when it’s no longer than 3″ (1/3 of 3 is 1 – cut 1″ or less each mowing).

Cutting too much of the leaf tissue off at one time can cause excessive stress on the plant. This can be harmful particularly under already-stressful conditions such as summer heat, drought, fungus and disease, and insect damage.

When the 1/3 rule is broken, the lawn will take on slight gray hue, losing much of the dark green color it once had.

If your lawn is overgrown, there’s some things you can do to help limit the stress and light hazy appearance:

  1. Mow at the highest possible setting and bag your clippings
  2. Mow in the opposite direction at the next lowest setting, and mulch your clippings
  3. Spoon feed some fertilizer (like Carbon Phix) to help promote new growth (about 1/4 lbs. Nitrogen per 1,000)
  4. Incorporate micronutrients including amino acids, fulvic acid,, sea kelp, and iron with products such as Green Lawn & Turf
  5. Plan the day before rain, or irrigate with some water immediately after

Lawn Mowing Best Practices (Tips)

  • Mowing your lawn frequently – this promotes healthy growing and a lush lawn
    • Cuts smaller pieces of grass and promotes proper mulching
  • Mowing height – cut your grass taller in the warmer summer months
  • Clean the mower deck – this can prevent any disease or fungus spreading onto healthy leaf tissue
  • Always use a sharp, clean, and balanced lawn mower blade
  • If using a lawn roller or striping kit, adjust your pattern every 2-3 mowing

Hope this was helpful and helped answer “what is the lawn one-third rule?” Proper mowing may be the single-most important factor to your overall lawn care program. Follow these simple lawn mowing tips, avoid breaking the 1/3 rule, and you’ll be off to a great start!

What is the 1/3 rule?

The one-third rule means to never mow more than 1/3 of the grass blade at a time in a single mowing. Example, if you keep Turf Type Tall Fescue at 4′”, mow the grass before it exceeds 6″. Similar example if you keep a low 2″ cut on Kentucky Bluegrass, cut the turf when it’s no longer than 3″.

What height should grass be cut in the summer?

For cool season lawns, it’s best to mow higher in the hot summer months. Rule of thumb, use the second highest setting on your mower. Mow at 3″ – 3.5″ in the summer for lower cut grasses like Kentucky Bluegrass (KBG), and up to 4″ – 4.5″ for grasses like Turf Type Tall Fescue (TTTF). Longer grass will help shade the ground, keeping the soil cooler. It will also help reduce heat and drought stress.

What is the best length for grass?

Depending on the type of grass you have in your lawn. Kentucky Bluegrass (KBG) and Perennial Ryegrass (PRG) can be cut short, around 2.5″. Some cultivars can even be “trained” to be cut very short using a reel mower (1″ and under). While other grasses such as Tall fescue (TTTF) prefer to be mowed higher, around 3.5″ – 4″.

Should I leave grass clipping on my lawn?

When properly mulched, grass clippings can be beneficial to lawns as they act as a natural fertilizer. Returning the nutrients from the mulched grass blades can decompose at the thatch layer and feed the soil and turf. However, if grass clippings are cut too long, breaking the 1/3 rule, then the longer grass clippings can do more harm than good, and is best to use a bagger.

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