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During the warm months when my grass is growing, is there a mowing schedule I can use to encourage the lawn to be green and healthy? Mine often seems "unhappy" when it's been cut (goes pale, some browning), which makes me want to mow it less-often.

Is there anything I can check to know when it's best to cut the grass?

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How MUCH you mow is often more important in my experience than how often, I think the guideline is never mow more than 1/3rd of the total length. This also is adjusted for grass, time of year and relative conditions (watering, latitude and so on), so lots of options. Although I tend to keep my grass a little long, I always mow to about 3" more due to kids and I am trying to prevent weeds from growing as well. –  MichaelF Jun 29 '11 at 13:55
I have a reel mower, so it's pretty easy for me: if it looks like it needs it, do it, otherwise I need to use a weed cutter to get the grass down, and then mow. –  Michael Todd Jun 29 '11 at 14:14

11 Answers 11

up vote 24 down vote accepted

It doesn't matter so much how often you mow, as much as how long the grass is.

If your lawn looks yellow and dried out after you've mowed it, you probably have the blade on your mower set too low. Some people like a super-short lawn like a putting green, but doing this requires both a specific variety of grass and lots of extra care spent on fertilizing and other upkeep. Since you're probably not one of those people, your grass will be healthiest if you let it grow a little longer.

The first time I mow my lawn in the spring, I mow it on the longest setting. Subsequently I'll mow about every 1-2 weeks, depending on how much rain we've gotten (I don't ever water the lawn--we get plenty of rain where I live), moving the blade a little lower until it's on about the middle setting. Recently I've noticed that my lawn is looking a little yellow in patches, so I'm going to let it grow a little longer, then move the blade back up. If your lawn is in a similar state, you'd probably benefit from doing the same.

Conveniently, somewhat longer grass is also more comfortable to walk on barefoot.

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There are several things that suggest the answer to your question is "the more often the better" and that your reaction to mow less frequently because of the yellowing you see after is the opposite to what you want for a green lawn.

First of all, we all know that for a lawn to be green it must be growing. Grass pales and turns yellow over time unless it is growing.

Second, the key factor to keeping a growing lawn healthy is mowing it according to its growth.

Therefore, if you get it growing quickly (fertilizer, lots of rain, etc.) then you simply need to be mowing more often.

The faster the growing, the more mowing is needed, but the greener the lawn.

As MichaelF pointed out in the comments, most advice for a healthy lawn says to follow the one-third rule: Never cut more than one-third of the height:

If your grass is growing, you’ll be mowing. Each grass type looks best and stays healthiest at a certain height. Use your mower to maintain that height as closely as possible. Cutting your lawn too short can be just as damaging as letting it grow too tall. The basic rule of mowing is to never cut more than one-third of the leaf blade. Generally, this means mowing about once a week.

(Source: http://www.gardenideas.com/lawns/lawn_perfect.html)

In other words, it's true that mowing can be unhealthy for the lawn, especially if the lawn was cut too short within too short of a time period. In other words, you want to be consistent about mowing, and if you get it too long, you should only cut off 1/3 the next mowing and then gradually reduce the height (as JSBangs posted).

Another factor in this equation is the optimal height for your type of lawn. Mowing for Dummies has a good table for this (and also echoes the one-third rule).

So, when you decide to mow less frequently because of the yellowing you see, you are actually perpetuating the problem. Grass is greenest at the top of the blade, and when you let that grow longer than it should, you cut off the healthiest part. In other words, it's not the act of mowing that hurts it, it's cutting too much of the blades. Mowing the next day shouldn't hurt at all -- as long as the blade is sharp!

There are a few other reasons that mowing as often as possible is the healthiest for your lawn:

  1. Ever seen a golf course's lawn? They do use different types of grass than most residences, but the mowers are usually out every day. They cut a tiny bit at a time, and the grass always stays healthy. (Of course they are growing it quickly with lots of fertilizer and watering.)
  2. Mulching is well known as a means to help improve the health of your lawn. The point of mulching is to turn what you clip into tiny shreds that simply fall back into the lawn. Many lawn mowers can do basic mulching if you remove the bag and apply a mulching blade. Cutting more often gives you a higher chance of returning small pieces to your lawn, instead of long pieces which may not be good for your lawn.
  3. I'm still looking for the reference, but I once read that "the secret" to a healthy lawn is "mowing twice a week".
  4. Another piece of advice I received from a lawn care center was "Mulch twice, bag once". You won't want to be mulching long grass (as above) so you'll need to be mowing often to follow that schedule.
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JSBangs is right on about not over-cutting. Some other important considerations are

  • Keep your blades sharp to prevent any tearing whatsoever. Put away the string trimmer when your lawn is having problems.
  • Get a testing kit to check the fertility and pH of your lawn area and correct if needed.
  • Keep the grass long enough to shade the roots in hot months.
  • Encourage deep roots by watering deep and less often if you do need to irrigate.
  • Prevent stressors such as weed competition and grubs.
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I found a few university studies that showed the healthiest height for most types of grass is about 3 inches. Depending on where you live, though, this may not be practical. Some towns and HOAs have a grass height restriction that is somewhat lower.

The other thing I've found from multiple sources is that you don't want to remove more that 1/3 of the height of your grass in a single cutting. If you chop off too much at once, it stresses the grass. (This may be your problem.)

If your lawn is really tall, and you need to get it down to the desired height, you may need to do multiple mowings, removing 1/3 of the grass each time. (Wait a few days between each mowing.)

So, if you are targeting a 3 inch grass height, you should mow whenever your lawn reaches 4.5 inches. As to how often you should mow to achieve that, it will depend on how fast your lawn grows.

One other thing to consider: If you have a huge riding mower, the tires will also be rough on the lawn. So, if you have to mow very often (once a week or more), you may end up harming the lawn. In that case, you may need to deviate from the above guidelines a bit.

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+1 for "you don't want to remove more that 1/3 of the height of your grass in a single cutting". & +1 for recommending 3inch (75mm) for finished cut height. Side note: 3inch (75mm) only applies to cool season lawns, warm season lawns have different (lower) grass height requirements. –  Mike Perry Jul 20 '11 at 21:41

I mow lawns for business and you should never cut more than 1/3 of the grass plant off (or you could damage the stem) and should mow at a height of 3 to 3-1/2 inches to keep the lawn healthy and green. Also, remember that it isn't really how tall the grass is that matters, unless it is more than 4 inches, it is the even cut.

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It really depends on a number of factors, such as:

  • Grass type eg Warm-season lawn or Cool-season lawn.

  • Growing conditions ie Are the conditions favourable to a healthy growing lawn:

    • Weather eg Temperature, rainfall...
    • Do you fertilizer your lawn? If yes, how? Naturally (organically) or with Chemicals?

Below are a couple of quotes from this answer I posted here on SE. Hopefully you find them of some benefit:

  • Mow high and when doing so only remove approximately ⅓ of the grass blade height. In my case, 3inch (75mm) is my final cut height, that is as high as my current lawnmower will cut. My next lawnmower will be able to cut to at least 4inch (100mm).
  • Seeing as my lawnmower is a mulching mowing, I leave all the grass clippings on the lawn (free, natural fertilizer), except with first cut and last cut of the season. I collect up those cuttings and dispose of them via a community yard waste pile.

You may also find the actual answer I pointed to above of some help:

What's an organic way to discourage crabgrass from a large “lawn”?

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I live in the UK, so it may not be the same in the USA, however there is a very simple guideline that works well.

Never cut of more than 1/3 of the grass when you mow the lawn.

So if you wish to have short grass then you need to mow more often. Likewise if you over feed your grass so it grows very fast you need to mow more often.

In the UK, a golf green needs to be mowed most days, as it is kept very short, but a normal back garden lawn can be kept neat and tidy without undue stress to the grass just by mowing it most weeks.

(Grow regulators (eg Primo Maxx) can allow short grass without having to mow every day.)

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I read recently that the commonly-accepted advice to remove no more that 1/3 of the grass height in a single mowing is actually based on grazing pasture research in the 1950's. Modern lawn and turf grass mixes are different from pasture grass mixes, and grasses react differently uniform mowing as compared to grazing. I keep my lawn long, and routinely remove up to 1/2 half the grass length without damage.

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If your lawn is stressed after mowing, you may need to sharpen your blade. Or you're cutting it too short. A lot factors into how often you need to mow. It should grow enough so that when you mow, you cut ⅓ of its length, leaving 3½ inches. Regardless, I cut my grass every 2 weeks on my mower's highest setting.

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I agree with 3 - 3.35 inches, but that varies depending on whether, and weather, I can mow every week. If rain interrupts the mowing and the lawn gets longer than normal, then I mow it longer to maintain the 1/3 rule; then I mow it again a few days later to bring it back to 3" or so. I say "or so" because my wife likes it shorter. I don't argue with her; I just cut it as close to 3" as possible; although I would rather it be longer, even to 4", to shade the roots and because it also needs less water then and browns less. The only time I mow it shorter, to 2.5" is on the last mow of the year; which in NE is sometimes into early December.

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As other's have stated, try not to mow off more than 1/3rd of the length of the blade.

Most cool season grasses like to be mowed high. 2-3" is a good mowing height. The blade is where it makes it's food (photosynthesis) so if you cut too much off it goes "hungry".

A lot of times when people complain about the lawn looking bad after cutting it's because they're cutting it too short and letting it get too long before cutting. The top of the grass that gets ample sunlight is a darker green than the base of the plant. If you let it get too high you're then exposing the parts that didn't get much sun. Someone in my neighborhood lets their grass grow long between cutting it. It always looks dark and healthy before being cut. After cutting it the color is lighter and has yellow patches.

Don't mow when temps are greater than 90 degrees and sunny. Or when the grass is wet. While the blade is damaged from being cut it loses more moisture and makes it more susceptible to disease. Making sure your mower blade is sharp helps produce a cleaner cut that heals faster. A reel mower, like you have, produces the cleanest cuts. I always swap my blades when the weather gets hot.

Waling on moist soil tends to compress it which causes other problems for the lawn so try not to walk on it when the soil is wet.

In the spring and fall your grass will grow faster (cool season grasses at least) than it does in the summer so you'll need to mow more frequently unless you water regularly.

It takes some thought to do it correctly. You have to monitor the weather. For example, if the grass doesn't really need to be cut right now but it's going to rain for the next 5 days you should cut it now rather than letting it get too long before you can cut it.

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