Height of Cut (HOC) Best Practice

[kentster]

I am wondering what best practice might be for HOC on lawns and what factors influence the decision. I've spent some time reading through old posts and it seems that we have a wide set of opinions and practices with anywhere from 1-5". It also seems that weather may be a factor, i.e. fungus issues, and time of year.

In my case, since becoming active on this forum early in 2018, my take away has been the higher the better, so I'm cutting at max height for my mower at 4". I'm also not using any sort of fungal control practices at this point and I don't have any irrigation.

This is the from the lawn maintenance guide in the articles area:

Always mow high at 3 inches or higher on a regular basis. Mowing high permits proper photosynthesis. That means the grass needs sunlight to grow. The shorter the blades of grass, the more you impede the photosynthesis process. Photosynthesis takes place at just about the middle of the grass blade. Ever notice the grass is yellowish closest to the soil? The reason is that as the grass utilizes sunlight to manufacture its own food, chlorophyll is produced to give the grass its green color. It is very important to remember you should never remove more than one third of the grass blade at a time or you shut down the food factory, which causes stress. You may wish to mow once a week or 2-3 times a week, depending on how fast the grass grows. Either is fine just so long as no more than one third is cut off at once.

Infrequent deep watering and frequently mowing high are the two crucial points of lawn care. Anything else you do is secondary to these cultural practices. Proper watering and proper mowing are what encourage a healthy growing environment for a lush green lawn that is able to crowd out weeds.

[HoosierLawnGnome]

The "best" height of cut is a combination of the time of year, how healthy the plant is at that height, the owner's aesthetic preference, and the intended purpose of the turf.

There isn't a hard and fast rule.

For KBG, taller turf has greater root mass. The plant likes to be bigger. The color has more time to develop on more mature blades and the roots dig deeper. It can take more damage from the sun. Thus "letting it out" towards summer is good for it's summer survival and to keep it looking good under stress.

Regular mowing that doesn't stress the plant is important at every HOC, thus the 1/3 guideline.

But what if you like the way it looks at a shorter height of cut? What if you are trying to make a better playing surface for a field sport like baseball? The goals change - you start making tradeoffs. At lower heights of cut, the grass looks much tighter and smoother, but it is a difference maintenance schedule and behaves differently.

Different fungi threaten it at shorter or taller heights. Root born disease will harm short turf easier. But, short turf dries out sooner so it doesn't struggle as much with some leaf born pathogens.

Taller turf survives pooling water better. Shorter turf will show chlorosis sooner.

But everyone has different goals, preferences, and challenges...

[john5246]

Isn't the height of cut dependent on the variety of grass?
For example, some types of grass can handle very low cuts, in that case you could cut really low with a reel mower. My perennial rye wants to lay down so I can't really go any higher than I am now.

[HoosierLawnGnome]

Let me make sure I'm not miscommunicating - taller KBG turf is generally healthier and easier to maintain. Most of the reasons people mow it < 2" (short for KBG) is for the aesthetic or performance of it for field sports.

But you lose color, durability, disease resistance, etc

Maintaining KBG < 2 in is much more challenging

[andy10917]

+1. There is no single "best practice". I slowly increase HOC as the Spring progresses, and some years I max-out at 3" or a little more, and some years I go to 4". As long as it stays healthy, I do what I feel looks best in current conditions.

[kentster]

+1. There is no single "best practice". I slowly increase HOC as the Spring progresses, and some years I max-out at 3" or a little more, and some years I go to 4". As long as it stays healthy, I do what I feel looks best in current conditions.

Andy, why do you slowly increase the HOC in the spring? Why not just start at 3"?

[andy10917]

I find that the lawn is denser/thicker and more upright if I raise it slowly to Summer height, and there is less BBDL ("brown blades down low") after the Spring Flush if it all got some sunshine as it woke up.

[kentster]

Ok, looks like I'll be staying at 4" for now... My goal at this point is to deepen the roots and crowd out weeds. With all of the rain and food I'm throwing down, the grass is definitely happy. We'll see how it is doing in August. That seems to be the test. Thanks guys!

[jcs43920]

It all depends on the type of grass and the time of year. This is how I do mine.

In the Spring

Kentucky Blue 3.25-3.5”
Tall Fescue 3.25-3.5”
Perennial Rye 2.25-2.75
Bluegrass/Rye 3”

In the Summer

Kentucky Blue 3.75-4”
Tall Fescue 3.75-4”
Perennial Rye 3”-3.25”
Bluegrass Rye 3.25-3.5”

[northeastlawn]

[quote=kentster post_id=333919 time=1559516109 user_id=9027]
Ok, looks like I'll be staying at 4" for now... My goal at this point is to deepen the roots and crowd out weeds.[/quote]

I always figured a thicker lawn crowded out weeds?

KBG probably likes a more frequent/lower cut to spread, other lawn types still like a lower cut to tiller out. A HOC of 4" works well if the lawn is very thick, but if you have thin sports, a lower cut helps thicken it out.

I get that the 4" HOC will block out more light, but if you have thin spots the weeds can just grow higher, if there is nothing taking up space in the bare spots.

Im trying to get the KBG to spread into some bare spots, Ill keep it at 2-2.5" until farther's day, then raise the mower a notch each week until the lawn stops growing or i run out of notches on the mower.

I always figured 2.75" was my prefect HOC when August's humidity hits. Ill usually have it a 3.5", then the disease hits and i just have to dry it out by lowering the mower a notch or two. But since were in August the lawn doesn't really grow fast enough to get back to 3.5"

Fall it goes back down to 2.5", then the following spring a 2" cut to clean it up.

Then we start all over again :-)

[jcs43920]

Yeah I think 4” is perfect if your goal is to grow deeper roots and crowd out the weeds.

[HoosierLawnGnome]

One thing I've noticed is that weeds that dont handle being cut short dont do well at lower heights of cut, but then others that would normally be suppressed by a taller, thicker canopy do better.

Clover and chickweed do better at lower HOC.

Dandelions and wild onion not so much. Quackgrass is hard to see.

Sedgegrass is a good inch taller by the 2nd day after a cut.

[kentster]

One thing I've noticed is that weeds that dont handle being cut short dont do well at lower heights of cut, but then others that would normally be suppressed by a taller, thicker canopy do better.

Clover and chickweed do better at lower HOC.

Dandelions and wild onion not so much. Quackgrass is hard to see.

Sedgegrass is a good inch taller by the 2nd day after a cut.

I'm sorry, but I am not understanding... "Clover and chickweed do better at lower HOC." Does this mean that lower HOC means more clover?

[ken-n-nancy]

I'm sorry, but I am not understanding... "Clover and chickweed do better at lower HOC." Does this mean that lower HOC means more clover?

Let's say that some clover seeds blow into your lawn. Much clover likes to grow to a height of about 2 inches or so.

If your grass is mowed at a 4" height, those clover seeds germinate, send out those first few leaves up to a height of 2 inches from the ground, but there isn't much light there with all the tall grass blades going up to four inches off the ground, so the clover doesn't do very well due to a lack of light. The clover seedlings kind of struggle and may even die out due to lack of sufficient light for photosynthesis.

If your grass is mowed at a 2" height, those clover seeds germinate, send out those first few leaves up to a height of 2 inches from the ground, where they get plenty of light, since they are up at the tops of the leaf blades. The clover seedling gets enough light to develop better roots, make more leaves, send up more stalks with leaves, make flowers, etc.

Basically, if the grass is mowed at 2" high, clover is quite competitive with the grass. If the grass is mowed at 4" high, the clover won't be as competitive with the grass.

[HoosierLawnGnome]

Ken n Nancy are right on.

Clover I'm certain has more of an edge at my HOC. Sedgegrass too.

Things that like to grow tall not so much. If a wild onion never gets 3 inches tall it doesnt do well.

[kentster]

Got it... Thanks Ken and/or Nancy!

[bpgreen]

I cut my lawn at 4" and my clover does fine. I'm often cutting at least some clover when I mow. Much of my clover is strawberry clover, but it looks about the same as Dutch white and I've got some Dutch white in the mix, also.