Understanding your lawn mower height settings and how to adjust your mower deck properly will help you get the most from your lawn. Mowing your lawn at the correct height improves your lawn’s health and appearance. Proper mowing can also helps prevent weeds from germinating.
In this article, I’ll explore how you can find the right mower height for your mower (and grass type), and provide some basic instructions on how to change your mower deck height for different kinds of mowers.
I’ll also explain why different height settings exist on mowers (and when you might need them), and what the science says about the importance of dialing in your mower deck height.
Finally, I’ll tell you exactly how to use your mower deck settings effectively to get the best results when using your lawn mower.
Let’s start with the absolute basics.
3 Inches or Taller is (Usually) the Best Mower Height Setting
When choosing the right height for your mower, the time of year is one of the biggest factors that will determine the mower height setting you should use.
I recommend that most people increase the mower height to a minimum of 3-inches from the middle of April through September. Depending on your mower, this might be its highest setting.
Lawn Experts Agree (and the science backs it up)
Dave Smitley, PhD, a professor emeritus in the Department of Entomology at the University of Missouri, supports this advice, sharing that “trying to mow your lawn at a height less than 3 inches is actually stressful to your lawn and may result in the need to apply more insecticide and herbicide.”
Basically, letting your turf grow tall improves health, and creates a better canopy to block weed germination.
But why else would you keep your mower setting at 3-inches, which is often the tallest setting?
Keeping your mower set this high will:
- Help the lawn conserve water
- Promote the development of deep digging roots
- Boost turf density
- Improve turf color
Sam Bauer, an Extension educator at the University of Minnesota, agrees, saying that for most typical Midwestern lawns it’s best to “maintain a height of 3 inches or higher.” He prefers this height due to the ability for taller grass to shade out weed seeds and keep soil cool, and also because “taller grass means longer roots and greater ability to withstand drought and reach nutrients.”
Exceptions to the Rule
The only times when you shouldn’t use this high setting is when you are doing the first and the final mow of the season. At these times, a 2.5-inch mowing height is best for most cool-season lawns (though at the end of the year I’ll sometimes go lower because of how I clean up my leaves).
Many homeowners imagine that the middle setting is best for their lawn, but this isn’t the case. In most cases, it’s too short. You should almost always go with the highest setting.
Some exceptions exist, however, based on your grass type. Some types of turfgrass look and grow best when mowed shorter than the recommendations I’ve detailed above. Bermuda is just one example. Often used for golf courses, Bermudagrass can thrive when mowed frequently at a low height.
There are several other warm season grass types grown in the southern US which will perform well when mowed at a shorter height. For many cool season lawns, mowing high will benefit the health and appearance of your lawn.
Tall Grass Promotes Deep Roots
When your grass is allowed to grow taller, the plant will develop deeper roots. The roots of your grass will usually grow approximately three times as deep as how tall it is.
When grass is mown to one inch high, the roots will usually only extend to about 3-inches deep. At two inches high, the roots dig to about 6-inches deep. At three inches high, the grass roots can dig as deep as 9-inches.
Deep roots are the key to a dense and healthy lawn. Your grass will be able to access water deep in the soil between rainstorms, will retain its green color longer during the dog days of summer, and generally be more healthy and resilient.
Mowing Schedule for a Lawn Kept Tall
It’s best to mow your lawn once weekly and never take off more than 33% (or one-third) the height of the grass blade.
If you mow less frequently, you might find yourself taking off more and this, which is bad for the lawn.
Also, taking off only a little a time is good if you want to leave the clippings on your lawn for extra nutrition. If you leave too thick a layer of clippings on your lawn you can end up with thatch buildup, or even smother and suffocate your lawn.
Why Have You Seen So Many Short Lawns?
Given how important it is to keep your lawn relatively long, you may wonder why so many people go the opposite route and cut their lawns short. There are a few different reasons:
Some people think a lawn that is cut on a short setting has better aesthetics than a taller lawn. Of course that’s subjective, and what’s attractive to one homeowner isn’t to the next.
But what’s universally true is that the preference for a short lawn will often negatively affect the health of that lawn.
When a lawn is cut short, it is thinner, needs more water, is more prone to weeds, and will have shorter roots. It will also probably not have that ideal green color we all want.
Confusion Over Lawn Mower Height Settings
As mentioned earlier, many homeowners assume that the middle height setting on their lawn mower must be best. If you don’t know the proper height setting, go with something average, right?
Wrong. The highest setting is often the best one for your grass. And remember that the numbers you see on the settings (if your mower has numbers) don’t link with the lawn cutting height.
Always remember to put your mower on the highest setting or to cut your grass at a minimum of 3″ to ensure your lawn stays healthy.
Many people admire the look of green golf course grass and assume that if they cut their lawns the same way, they will have the same wonderful green color.
This is a mistake, as golf courses actually use special kinds of grass that allow them to keep their courses cut so short.
Most homes have lawns with grass that cannot thrive when mowed so close to the ground.
How to Change the Height Settings on Your Mower
The first step when you want to change your mower’s height settings is to consult with the manual.
The manufacturer’s manual will have information on how to increase and lower the setting of your mower. The way to adjust the mower and what the different adjustments mean vary from brand to brand of lawn mower.
A common mistake is to just assume that you understand all the ins and outs of your mower. You’d be surprised at the features and nuances you can learn when you take a few minutes to read the manual.
Once you understand the instructions in the manual about how to change the settings, do the adjustments on a flat surface. You will need to put the mower on a flat surface to see how low or high the mower is. A flat pavement surface (driveway) or a garage is a great place to do this.
And don’t make the mistake of thinking that the bottom of your mowing deck is the height at which your grass will be cut … your mower’s blade is usually higher.
Pick Settings Based On Your Grass
As we’ve already mentioned, most types of grass grow best with the highest setting on most mowers.
If you aren’t sure, or are unhappy with the results at this setting, I recommend starting high and then adjusting the deck lower one setting at a time until you get to a mowing deck height you’re happy with.
Before you start making your adjustments, ensure the mower is completely turned off and will not turn back on. That is an essential safety precaution and crucial for preventing injury.
If you have a gas mower, you will find a safety catch to hold down for the mower to run. Ensure that this is not being pressed by any kind of object. It’s best to remove the spark plug from the mower so that there’s absolutely no possibility it can start.
Many modern push mowers (and even some reel mowers) can make height adjustments just by moving a lever. Some types of mower may require adjustment of each wheel one at a time. If you have this kind of mower, ensure that you don’t inadvertently adjust each to a different height. If you do you’ll get an uneven mow job (or just go in circles).
You may need a wrench, screwdriver, and perhaps other tools to adjust wheel height.
Adjusting Height Settings on a Rotary Mower
As we mentioned earlier, the exact procedure for changing the setting on your mower will vary from manufacturer to manufacturer and model to model.
However, there are certain things you can keep in mind if you have a rotary mower, be it a push mower or self propelled.
If you have a very inexpensive or entry-level mower, it will probably have a very basic procedure for height adjustment. If you have an expensive model, it will be easier and faster to adjust.
One of the most basic kinds of height adjustment is axle adjustment. Using this method, you will physically take off the wheels and put them at a higher setting. This will usually involve a snap-in system. If you have a very inexpensive or entry-level mower, this is probably the system you will use for adjusting height.
Individual Wheel Levers
Another type of method some rotary mowers use involves individual levers.
Using this method, each of the mower’s wheels has an individual lever. You’ll use these to raise or lower the height. In order to level the mower, you will have to adjust each individual wheel to a uniform setting.
This is the type of mower deck adjustment my Honda self propelled mower has, and I find it very easy to use.
Single Lever System
If you have a high-end model or a riding mower, you might find it uses a single lever system.
This is easy to use and involves using one lever to raise the deck. You’ll find the lever to one side of the machine, frequently close to the axle.
The name of this system is often the “central single lever height adjustment system.”
Riding Mowers are Usually More Complicated
Adjusting the height settings on a riding lawn mower is usually more complex and can vary considerably from model to model. My best advice is to thoroughly read the owner’s manual that came with the riding mower to make sure you know what you are doing.
If you can’t find your manual but have the manufacturer and model number of your mower you can find and download the manual with a quick Google search.
When in Doubt, Set Your Blade High for a Healthy Lawn
Many experts explain that keeping your lawn taller (three inches or higher) is best for grass health, and I agree with them.
Mowing high will put your grass in a better position for dealing with conditions such as drought or hot weather. It is also helpful if your lawn has to deal with shady conditions.
When the weather gets a little cooler, you can usually cut the grass a little bit shorter if you want to. If you don’t know what kind of grass you have, a good rule of thumb is to cut it at three inches or down to a minimum of 2 ½”, never removing more than one third of the grass blade at a time.
Understanding your model of lawn mower and how your lawn mower height settings work is important if you want to use it properly. Read the manual that came with your mower to understand how its height settings work and how to adjust them.
Once you understand what to do and how to do it, you will know how to customize your mower for the healthiest lawn.
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- Mow high for weed and grub control by Dave Smitley, Michigan State University Extension (https://www.canr.msu.edu/news/mow_high_for_weed_and_grub_control)
- Mowing practices for healthy lawns by Sam Bauer, University of Minnesota Extension (https://extension.umn.edu/lawn-care/mowing-practices-healthy-lawns)