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Mowing: The Rule of Thirds

Set the mower to its highest setting this time of year on most grass species (except Bermuda, bentgrass or Seashore paspalum).

Set the mower to its highest setting this time of year on most grass species (except Bermuda, bentgrass or Seashore paspalum).

Here is a slightly humorous, somewhat agonizing letter pulled from the SafeLawns mail bag: “Someone in the family (I won’t say who) cut our combination new and old lawn with a very dull blade (electric mower) and not only did it once but twice on the same day! The 2nd time because the 1st time didn’t work so well! Our problem is that within a couple days the grass began to turn yellow down to the roots. Now we know why but we don’t know what to do about it. After all that work last fall I feel sick and panicky. I hope you can help us out with some advice as to how to undo the damage. Also, I’ve been reading about compost tea. We don’t have a compost pile. Is it OK to use Coast of Maine compost or compost and peat mixture? I truly appreciate any help you can give us. I should probably let you know that except for once last fall (weed killer) we’ve always used organic products on the lawn. Thank you.
Sincerely,
Jennifer Metheny

Well, Jennifer,
As you now probably know, your not-to-be-named lawnman essentially “hayed” the lawn by cutting too much of the grass at once — and then doing it again in the same day. I say “hayed” because that yellow-brown look of your lawn is how fields look after they’ve been cut to the ground.

Now, the good news is that grass is the most resilient plant on the planet and, most likely, it will grow back and be fine. What your we-can’t-name-him now lawnman has done, however, is opened up the lawn to pressure from all three: 1) weeds, 2) insects and 3) disease. So tell him not to do it again!

Cutting too much of the grass plant at any one time shocks the plant and it temporarily shuts down. The rule is to never cut more than one third of the grass blade at any one time. If the lawn does get too tall (like mine right now due to all the rain in Maine), it should be brought down to regular height in stages — say from 6 to 4 inches on one cutting. Then give the lawn a two or three-day rest before cutting it back to 3 inches.

You can give your lawn a dose of low nitrogen organic fertilizer right now, along with a drink of compost tea. There is a video on the SafeLawns.org web site about how to make this tea yourself. Coast of Maine Organics is a fine brand of compost made here in the Northeast; locally made compost should always be used if possible.

Folks should also water lawns that have been cut like this, but if you’re in Massachusetts, you probably got enough rain lately.

Best of luck.

About The Author

Paul Tukey

An international leader of the green movement, Mr. Tukey is a journalist, author, filmmaker, TV host, activist and award-winning public speaker, who is widely recognized as North America's leading advocate for landscape sustainability and toxic pesticide reduction strategies.

Number of Entries : 1023
  • peggy

    I’m really glad to see this post as I have a question about mowing.
    I keep hearing to let my grass grow tall and only cut 1/3 off.
    If the grass grows tall, and you mow it at highest setting, it will take off about 2/3 of grass and stress your grass out.
    I have a lot of clover and it gets really hard to get my mower through it if I let grass get high.

    The other problem is..If I let the grass grow tall, my mower will take off 2/3 of the grass even at the highest setting. My grass will look great, and then I mow and it starts to turn brown from stress. Happens every year when it starts to get warm. I was told I shouldn’t even cut my grass once it hits 80 degrees?..
    Please advise..thanks. I saw this mower called the billygoat? Wondering if I should have gotten that mower instead of a Toro?
    THANKYOU for any help you can give me.
    Peggy

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