How often can I cut 1/3

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RichS
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How often can I cut 1/3

Post by RichS » September 6th, 2017, 12:30 pm

Here's a 101 question that I haven't been able to find an answer to.

It seems obvious that if I cut 1/3 of the length of my grass, then turn around and cut it again at an angle, I've still cut more than 1/3. Waiting an hour doesn't satisfy the "don't cut more than 1/3" guidance. What if I make the 2nd cut tomorrow? 2 days later? 3 days?

During heavy growth, typically 3-4 weeks in the Fall, maybe once or twice in the Spring, I try to cut Friday evening and then again late Sunday. But if it's going to rain Sunday, how far can I move it up? Sunday morning? Saturday evening?

More curiosity than anything else.

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ken-n-nancy
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Re: How often can I cut 1/3

Post by ken-n-nancy » September 6th, 2017, 2:39 pm

RichS wrote:
September 6th, 2017, 12:30 pm
It seems obvious that if I cut 1/3 of the length of my grass, then turn around and cut it again at an angle, I've still cut more than 1/3.
I'm afraid that I'm not understanding what is meant by the above. In particular, I don't know what is meant by "cut it again at an angle?"

Is this second cutting at the same "height of cut" as the first cutting?

The 1/3 rule is really intended for a "steady state" situation, where all cutting is at the same "height of cut" (HOC). If you're trying to drop the height of cut, that's a special situation. I don't know that there's a standard guideline for that. To drop the height of cut without causing undue stress, I would recommend paying close attention to the grass, it's health, and how it's adapting to the gradual lowering of the height of cut -- I don't think a "standard rule" is going to apply, as there's just too many variables.
RichS wrote:
September 6th, 2017, 12:30 pm
During heavy growth, typically 3-4 weeks in the Fall, maybe once or twice in the Spring, I try to cut Friday evening and then again late Sunday. But if it's going to rain Sunday, how far can I move it up? Sunday morning? Saturday evening?
In this situation, though, I'm presuming that all the cuts are being made at the same height. Let's presume your cutting height is at 3". In that case, you'll want to cut the grass when it is no more than 4.5" tall, so that when you cut the 4.5" grass to 3" you've removed only 1/3 of the blade.

Let's say you cut the grass on Friday evening, so it's then at 3" height. You plan to cut it on Sunday night, when it is expected to be 4.5", but rain is expected, so you want to cut it earlier. Cutting it earlier cannot possibly exceed the 1/3 rule, as it won't be too tall yet. However, this is obvious, so I don't think this is really what you're asking.

I'm going to guess that what you're asking is what to do when it's time to mow the grass and you've let it grow more than 1/3 above your desired cutting height. Let's say your desired height-of-cut is 3" and you previously cut the grass last Sunday evening. It's now Friday evening, but the grass is 5.5" tall, since it grew a lot in the past five days in a period of heavy growth. To accommodate the 1/3 rule, the most you can take off is 1.83 inches. But, your mower only has 0.5" height adjustment, so you end up cutting at 3.5" (removing 2.0 inches, but that's the closest you could do) even though your desired cutting height is 3.0" Since you wanted to be at 3.0" but actually cut at 3.5", you'll plan to make another cutting soon -- on Sunday, when the grass is about 4.25" high. At that time, you'll reduce the height to 3.0" to get back to your desired height of cut. Is this the situation you are describing?

If so, your question is really how to drop the HOC to 3.0" when the grass is 5.5" tall. Clearly, making a 1st cut to 3.5" and then as soon as the whole lawn is mowed, changing the mower height to 3.0"; and then immediately cutting the grass at the new height doesn't really follow the 1/3 rule, as there was no time for the grass to recover between the 1st cut and the 2nd cut. On the other hand, waiting to make the 2nd cut until the grass has grown back to the height it was before cutting doesn't help you get back to the lower HOC.


The intent of the "1/3 rule" is to wait until the grass has grown tall enough so that 1/3 will be cut off to bring it back down to the desired HOC -- the "1/3 rule" is basically a "rule of thumb" that this approach has been found to work well. Your plan is fundamentally doing something different. You're trying to shorten the grass by more than 1/3 in a pair of cuttings spaced two days apart, and then allow the grass to grow for 5 days and then repeat the cycle. What you're describing here is not as desirable as the standard "1/3 rule" and is likely to give reduced results.

It seems to me that the 2nd cut of 1/3 height needs to be at least a couple days after the first cut. Trying to shorten that even further might be trouble. As to how much you can shorten it without seriously compromising the appearance of the grass is going to be very dependent upon the grass type, growing conditions, etc. It's going to be difficult to give a specific rule to apply. You're going to have to see how the grass responds to see what you can get away with, as you're already diverging from the "1/3 rule" in order to follow the weekly calendar as complicated by the weather!

RichS
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Re: How often can I cut 1/3

Post by RichS » September 6th, 2017, 9:56 pm

Yes, that's the situation. I cut to 3" last Sunday but it's 5+ by Friday. Only cutting 1/3 each week would result in ever higher grass.
Clearly, making a 1st cut to 3.5" and then as soon as the whole lawn is mowed, changing the mower height to 3.0"; and then immediately cutting the grass at the new height doesn't really follow the 1/3 rule
Yes, that was my into - cutting the lawn in one direction, then lowering the blade and immediately cutting it again in another direction (though the direction doesn't really matter). While each is <1/3, the grass biology isn't going to respect this linguistic gymnastics.

Unfortunately, I'm a bit confused with your 2 points-
What you're describing here is not as desirable as the standard "1/3 rule" and is likely to give reduced results.
- 2 days later is bad
It seems to me that the 2nd cut of 1/3 height needs to be at least a couple days after the first cut.
- you need to wait 2 days

At the end of the day, it doesn't really matter. I'm out of town Monday am through Friday mid-day, so 2 days of recovery is all I can do. I was just curious, having seen the recommendation many times without any timeframe attached.

JohnP
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Re: How often can I cut 1/3

Post by JohnP » September 6th, 2017, 11:23 pm

If it were me in your situation and I came home to 6" grass I would bag mow the first time and then mulch mow the second time and weather/time permitting I would just do it at the same time. Adjusting HOC accordingly to step nicely down to goal height, 3" or whatever.

I would just do it and see what my grass did, and enjoy the rest of my weekend at home not worrying about whether Mother Nature is going to let me mow again.

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ken-n-nancy
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Re: How often can I cut 1/3

Post by ken-n-nancy » September 7th, 2017, 11:49 am

RichS wrote:
September 6th, 2017, 9:56 pm
Yes, that's the situation. I cut to 3" last Sunday but it's 5+ by Friday. Only cutting 1/3 each week would result in ever higher grass.
Thanks for the confirmation that I was on the right track about your situation.
RichS wrote:
September 6th, 2017, 9:56 pm
Unfortunately, I'm a bit confused with your 2 points.
Sorry, I wasn't as succinct as I could have been!
RichS wrote:
September 6th, 2017, 9:56 pm
ken-n-nancy wrote:What you're describing here is not as desirable as the standard "1/3 rule" and is likely to give reduced results.
- 2 days later is bad
When the grass is really growing gangbusters (from 3" to nearly 6" in 5 days), the approach of a Friday evening mowing followed by a Sunday evening mowing isn't going to be good as mowing every time the grass has grown from 3" to 4.5". I wouldn't necessarily say your Friday & Sunday mowings would be "bad" though -- your plan would be significantly better than just a single mowing from 6" to 3" once a week!
RichS wrote:
September 6th, 2017, 9:56 pm
ken-n-nancy wrote:It seems to me that the 2nd cut of 1/3 height needs to be at least a couple days after the first cut.
- you need to wait 2 days
I think waiting two days after the first 1/3 cut before making another cut to a lower HOC would be sufficient (i.e. I don't think there'd be much benefit to waiting a 3rd day.) Waiting even one day, though, would be better than not waiting at all!
RichS wrote:
September 6th, 2017, 9:56 pm
I'm out of town Monday am through Friday mid-day, so 2 days of recovery is all I can do.
Seems to me that given your schedule, your plan of a Friday night mowing (removing about 1/3 of whatever height the grass has grown to) and then a Sunday night mowing (to further lower to your desired cutting height) is about the best you can do. I think your approach would definitely be better than just mowing once a week, particularly in periods of fast growth where the grass grows more than 1/3 of a blade height in a week!

What you describe is pretty much exactly what I do when coming home from a mini-vacation - an initial 1/3 mowing to something higher than my normal HOC, and then another mowing a couple days later to return to the desired HOC. It's definitely better than a single cutting from 6" to 3".

PS: We always do mulch mowing. (Well, unless scalping for a renovation.)

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