Cutting height for grass - Ask Extension
Do you cut grass low or high over the summer. I water about 40 minutes every other day. My grass is thin and isn't very green. Ph is in the good ran...
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Cutting height for grass #836069
Asked June 17, 2023, 12:51 AM EDT
Do you cut grass low or high over the summer. I water about 40 minutes every other day. My grass is thin and isn't very green. Ph is in the good range. I had heard that cutting grass short allows the lawn to thicken up. Thank you.
Lane County Oregon
Expert Response
Hello,
If your grass is thin and not very green, then you likely need to fertilize your lawn. A normal application of fertilizer for a healthy lawn would be 1 lb. of nitrogen per 1,000 sq. ft. If your lawn is thin and light green, then I would recommend 2 lbs. of nitrogen per 1,000 sq. ft. of a slow release fertilizer. Scott's Turf Builder Lawn Food (north) would work well. It has an N-P-K ratio of 32-0-4 with 66.6% of the nitrogen quick release and 33.3% slow release. Note: you could also make 2 applications of fertilizer spaced 1 month apart at a rate of 1 lb. of nitrogen per 1,000 sq. ft. using a quick release fertilizer like urea (46-0-0).
To calculate how much fertilizer, you need to apply to get 2 lbs. of nitrogen per 1,000 sq. ft., divide 2 by the decimal value of the nitrogen percentage. If we use Scott's Turf Builder as an example, take 2 and divide by 0.32 (the decimal value of the first number shown above). That equals 6.25 lbs. So if you apply 6.25 lbs. of Scott's Turf Builder Lawn Food to 1,000 sq. ft., you will apply 2 lbs. of nitrogen per 1,000 sq. ft.
If you prefer, you could also use an organic fertilizer. As an example, I found "Purely Organic Lawn Food (10-0-2)" on Home Depot's website. To apply 2 lbs. of nitrogen per 1,000 sq. ft. from this product, you would need to apply 2/.10 = 20 lbs. of fertilizer per 1,000 sq. ft. to get the same 2 lbs. of nitrogen per 1,000 sq. ft. because the nitrogen percentage is only 10 percent vs. 32 percent for the Scott's fertilizer. Additionally, many organic fertilizers only have 6 percent nitrogen.
To understand how mowing affects turfgrasses, you first need to understand that every species has a mowing tolerance range. If you go below the tolerance range, that grass cannot get enough energy from the sun to maintain density. Also, if you go above about 3 inches, your grass will start to thin out. So within a grasses tolerance range, the lower and more frequent you mow, the denser and finer the leaf texture will get.
There are a couple of requirements though. First, your lawn must have enough fertilizer and water to be healthy. And second, the lower you mow, the more frequently you will need to mow or else you will be cutting too much grass at one time which will stunt the growth because it will not be able to deal with a large loss of leaf area at one time. For example, if you want to mow perennial ryegrass at 1.5 inches, you will need to mow it 2x per week for it to look nice. And lastly, when growing grass in shade, you want to mow at the higher end of the mowing range because the grass struggles to get enough light.
The other big change that occurs when you mow lower is that the grass will have shorter roots. It is not a dramatic difference when you are lowering your mowing height from 2.5 inches to 1.50 inches (e.g., perennial ryegrass), but if you mow grass below 1 inch, the roots will get much shorter. If you grass has shorter roots, then you need to irrigate more frequently - which does not mean more total water. In fact, smaller plants use less water. But it takes more monitoring than most people are willing to do to water less because you need to hand water just the spots that are drying out when you are watering the correct amount. The reason is that irrigation systems do not put water down very uniform. So if you are not seeing some dry spots than a lot of your lawn is being over watered.
General mowing height ranges for different cool season grasses are as follows:
Perennial ryegrass: 1.50" - 2.5"
Tall Fescue: 2.00" - 3.0"
Chewings Fescue: 0.25" - 2.5"
Red & Hard Fescue: 1.50" - 2.5"
Kentucky bluegrass: 1.50" - 2.5"
Colonial bentgrass 0.50" - 1.5"
Creeping bentgrass 0.10" - 1.0"
Annual bluegrass 0.10" - 2.0"
Note: the lowest heights for chewings fescue, annual bluegrass, and creeping bentgrass are for golf course putting greens that get mowed 6 or 7 days a week.
I hope this helps. Good luck.
If your grass is thin and not very green, then you likely need to fertilize your lawn. A normal application of fertilizer for a healthy lawn would be 1 lb. of nitrogen per 1,000 sq. ft. If your lawn is thin and light green, then I would recommend 2 lbs. of nitrogen per 1,000 sq. ft. of a slow release fertilizer. Scott's Turf Builder Lawn Food (north) would work well. It has an N-P-K ratio of 32-0-4 with 66.6% of the nitrogen quick release and 33.3% slow release. Note: you could also make 2 applications of fertilizer spaced 1 month apart at a rate of 1 lb. of nitrogen per 1,000 sq. ft. using a quick release fertilizer like urea (46-0-0).
To calculate how much fertilizer, you need to apply to get 2 lbs. of nitrogen per 1,000 sq. ft., divide 2 by the decimal value of the nitrogen percentage. If we use Scott's Turf Builder as an example, take 2 and divide by 0.32 (the decimal value of the first number shown above). That equals 6.25 lbs. So if you apply 6.25 lbs. of Scott's Turf Builder Lawn Food to 1,000 sq. ft., you will apply 2 lbs. of nitrogen per 1,000 sq. ft.
If you prefer, you could also use an organic fertilizer. As an example, I found "Purely Organic Lawn Food (10-0-2)" on Home Depot's website. To apply 2 lbs. of nitrogen per 1,000 sq. ft. from this product, you would need to apply 2/.10 = 20 lbs. of fertilizer per 1,000 sq. ft. to get the same 2 lbs. of nitrogen per 1,000 sq. ft. because the nitrogen percentage is only 10 percent vs. 32 percent for the Scott's fertilizer. Additionally, many organic fertilizers only have 6 percent nitrogen.
To understand how mowing affects turfgrasses, you first need to understand that every species has a mowing tolerance range. If you go below the tolerance range, that grass cannot get enough energy from the sun to maintain density. Also, if you go above about 3 inches, your grass will start to thin out. So within a grasses tolerance range, the lower and more frequent you mow, the denser and finer the leaf texture will get.
There are a couple of requirements though. First, your lawn must have enough fertilizer and water to be healthy. And second, the lower you mow, the more frequently you will need to mow or else you will be cutting too much grass at one time which will stunt the growth because it will not be able to deal with a large loss of leaf area at one time. For example, if you want to mow perennial ryegrass at 1.5 inches, you will need to mow it 2x per week for it to look nice. And lastly, when growing grass in shade, you want to mow at the higher end of the mowing range because the grass struggles to get enough light.
The other big change that occurs when you mow lower is that the grass will have shorter roots. It is not a dramatic difference when you are lowering your mowing height from 2.5 inches to 1.50 inches (e.g., perennial ryegrass), but if you mow grass below 1 inch, the roots will get much shorter. If you grass has shorter roots, then you need to irrigate more frequently - which does not mean more total water. In fact, smaller plants use less water. But it takes more monitoring than most people are willing to do to water less because you need to hand water just the spots that are drying out when you are watering the correct amount. The reason is that irrigation systems do not put water down very uniform. So if you are not seeing some dry spots than a lot of your lawn is being over watered.
General mowing height ranges for different cool season grasses are as follows:
Perennial ryegrass: 1.50" - 2.5"
Tall Fescue: 2.00" - 3.0"
Chewings Fescue: 0.25" - 2.5"
Red & Hard Fescue: 1.50" - 2.5"
Kentucky bluegrass: 1.50" - 2.5"
Colonial bentgrass 0.50" - 1.5"
Creeping bentgrass 0.10" - 1.0"
Annual bluegrass 0.10" - 2.0"
Note: the lowest heights for chewings fescue, annual bluegrass, and creeping bentgrass are for golf course putting greens that get mowed 6 or 7 days a week.
I hope this helps. Good luck.
Brian,
Thank you very much. This is very helpful. I had a followup question. Are you measuring the cutting height from the ground? If I were to take a tape measure and measure from the ground up would that be correct?
I really appreciate your help.
Joel
Joel Robe
Hi Joel,
Good question. No the cutting height is measured on the mower. Measure from the bottom of a wheel to the blade. You have to be a bit creative to do this. For example, set the mower on 4 chairs, or put two wheels on a work bench and have someone hold up the other side as you measure.
The other thing I forgot to mention is that in the winter, the ground can get a little soft so the mower will sink in a little bit. It is not a bad idea to raise the mower one notch higher. It also helps the plant get a little more light when the days are shorter.
Good luck.
Good question. No the cutting height is measured on the mower. Measure from the bottom of a wheel to the blade. You have to be a bit creative to do this. For example, set the mower on 4 chairs, or put two wheels on a work bench and have someone hold up the other side as you measure.
The other thing I forgot to mention is that in the winter, the ground can get a little soft so the mower will sink in a little bit. It is not a bad idea to raise the mower one notch higher. It also helps the plant get a little more light when the days are shorter.
Good luck.
