Some people love mowing their lawns. Every Saturday, they sit on their lawnmower, turn the machine on and lose themselves in the dream world of riding a white steed across the prairies.
Other people just want the job done so the neighbors do not complain about the jungle, and pay the local kid to do it. One way or another, you need to know: How high should I cut my grass?
There is a lively debate about the length of each blade of grass. Nevertheless, some scientific rules should be followed in order to maintain the lawn in the best shape and health. Apparently, the length of your grass is more important than we give it a credit.
The rule of thumb
The rule of thumb for the right grass height is what most experts offer. What that means is that it is not strictly accurate and not applicable for every situation. As we go on with different opinions, we will find out just how much truth this is, as well as why the strict number of inches for your grass is not appropriate.
Most experts suggest that an optimal height for a cool-season grass is about 2 1/2 inches. They also agree that every time you mow your grass, you should only be cutting about 1/3 of each grass blade. They also suggest that the best time to mow your lawn is when your grass is 3 2/3 inches high, more or less.
But, it is not that simple. Different types of grass and different climates have different factors that affect just how high should you cut your grass. On top of that, different experts have different opinion, with a full justification:
Why exactly two and a half inches?
The season in which you mow your lawn also affects the height of your grass, but it is highly recommended to stick to the two-and-a-half-inch rule of thumb in fall and, maybe in spring, but not as important. In summer, if you cannot remember just how much should you cut, it would be less of a mistake to leave it taller, than to cut too much.
When the weather really heats up, leave it high until the beginning of the fall season when the weather cools off a bit.
Why, you must be asking. Why are those 2 1/2 inches just the right grass height? You are trying to solve two problems and achieving a balance. Mowing the grass stimulates its growth, just like “pinching” a tomato plant. If you allow the grass to get too tall, you are not stimulating good grass growth and missing the opportunity to make your lawn more resilient and healthier. On the other hand, if you cut the grass too short, what is called “scalping,” you stress the plant too much.
While the 2 1/2-inch height rule works for cool-season grass and works well for the fall mowing, it is definitively not a figure set in stone that you must follow throughout the entire mowing season.
For example, If you are attempting to eliminate crabgrass, you may wish to leave the grass taller, up to three inches, in spring and summer. During these two seasons, crabgrass competes with your lawn for space. The longer grass provides extra shading which will sufficiently hurt crabgrass to prevent it from multiplying. In fall, when the frost kills more sensitive crabgrass, you can go back to cutting your grass to two and a half inches.
How do you measure your grass?
Once you accept the two-and-a-half-inch rule, you will want to make sure you are following it. If you start walking around your lawn with the measuring tape, your neighbors will start worrying about your mental health. There are easier ways.
The easiest way and the most popular one is to draw a line on one of the tires of your lawnmower so when you are ready for mowing your lawn, you will know just how much higher your grass is than the marked line and adjust your mower to the right height.
Some people mark the line for the right height of the grass on the deck post, where they can see it clearly. So, when the grass is about 1/3 inch over that line, it is time to take out the mower.
The factors that affect the rule
1. Grass variety
We have already established that cold weather grasses grow at a different rate than warm weather grasses. But, on top of that, every grass type has its own perfect mowing height.
What that means is that you need to learn about what your particular grass needs, what is its specific mowing requirement and then maintain your grass at that height. It is well worth a bit of research since the knowledge will reward you with healthy, verdant thick grass free of weeds and resistant to the summer drought.
2. Keeping the weeds away
For the longest time, there was a firm belief among lawn owners as well as experts that the shorter the grass, the less often you have to mow it. We know better now. All that ‘scalping” achieves is space for the weeds to grow and for the heat and drought to kill your grass.
3. Keep the bugs away
If you let your grass become too high between mowing, you are potentially creating a perfect habitat for bugs such as mosquitoes and wild critters such as mice, voles, and snakes. On top of that, too long grass is difficult to mow and long grass clippings have to be removed and cannot be left on the lawn.
4. Laziness does not pay
The additional effort to mow your lawn frequently to maintain the optimal height really pays off. It is not such a big effort. Even at the grass peak growth, you probably need to mow it once a week max. Of course, the frequency of mowing depends on your grass type and its optimal height, and its growth speed, which changes depending on the weather conditions.
For example, cool-season grass such as Kentucky bluegrass and fescues grows faster during the cool spring and fall weather. While exact heights vary depending on the grass type, the range for cool-season turf is between 1 and 4 inches.
Warm-season grasses such as St. Augustine, centipede, Bermuda, and zoysia are at their fastest growth in the height of summer. Exact grass height vary depending on the grass type and can vary even for the same grass but different type.
For example, Empire zoysia should be kept between 0.75 and 3 inches, but Zenith zoysia does best if left at 1.5 inches. Even those rules vary depending on the region where you live.
We come back to the general rule of thumb: never cut more than one-third of each grass blade at each mowing. The simplest way to do that is to learn what your particular turf’s optimal height is, then allow it to grow longer by one-third before mowing it.
Ideal grass height by type
DIY Network produced this handy list of ideal grass heights depending on the variety of grass:
- Bahia: 2.5 to 4 inches
- Bermuda: 0.5 to 2.5 inches
- Buffalo: 1.5 to 4 inches
- Centipede: 1 to 2.5 inches
- Kikuyu grass: 1 to 1.5 inches
- St. Augustine: 1 to 3 inches
- Zoysia: 0.5 to 3 inches
- Fine fescue: 1.5 to 4 inches
- Kentucky bluegrass: 0.75 to 3.5 inches
- Perennial ryegrass: 0.75 to 2.5 inches
- Tall fescue: 1.5 to 4 inches
Some quick rules
- Allow grass to grow higher in summer and during the summer drought, regardless of the kind of grass;
- Cut warm-season grass shorter in spring so you can remove dead grass;
- For the last fall mowing, cut cool-season grasses shorter if you live in regions prone to snow, to prevent snow mold;
- Grasses that grow in shade should be allowed to grow taller.
Different experts – different rules
You do not have to agree with it. Pete here does not. He also explains a bit of science about the plants and the reason for the specific rules about the height of grass:
Mowing lawn every Saturday might be convenient for you, but it is not so good for your lawn. Just when you should mow your lawn should depend on the height of the grass and not on your schedule.
Also, you cannot count on the interval between two mowings to be your guide. Do you know what happened since the last mowing? Did it rain? Was it too hot?
It is a fact of life that grass growth depends heavily on the weather. Grass will have a sudden growth spurt after it rains. If there is no enough rain, it might barely grow at all.
So, the mowing schedule is really not practical. This means that there will be times when you have to mow your lawn every week, and then you might go weeks before you have to get out your lawnmower. Let the grass dictate what it needs, you will benefit ultimately from the healthy, green lawn.
When to mow
It might not be convenient for your lifestyle, but the best time you should mow your lawn is early evening if the lawn is dry and it hasn’t rained recently. If you cut your grass in the morning, it might still be wet with dew. Wet grass will play havoc with your lawnmower and can clog it.
If you mow just before the hottest time of the day, you will leave the grass too stressed. Cutting it is already stressful on the grass. If you cut it in the early evening, the grass has enough time to recover before the next day’s heat.
It appears that the question: how high should I cut my grass is not that straightforward. Nevertheless, there are some conclusions you can have that will help you make your own informed opinion about how high your grass should be:
- Most experts advise keeping your lawn about two and a half inches tall most of the year. That height differs depending on the kind of grass as you can see from the chart.
- In the spring, it is suggested to leave the grass slightly taller – about three inches, to prevent crabgrass and other weeds from taking over.
- While experts do not agree about the ideal height of the grass, they do agree that you should only remove the top one-third of the grass. This light trim tends to stimulate grass growth without stressing the grass too much. It also ensures that the grass is tall enough to keep weeds at bay.
- Another rule experts agree on is to never cut grass below two inches. It would expose it to too much heat and to the weeds to take over.