Follow these tips on the last mow of the season so you can protect your lawn during the winter and see a quick recovery in early spring.
For most of us, at some point during the late fall or winter, our lawns will enter a period of dormancy. A lot of questions come up at this time as homeowners wonder what’s the best way to prepare their lawn for this period of dormancy. The most popular questions usually relate to how high should your last mow of the season be and when should you stop mowing your lawn before winter. The answers are simple, yet there are some differences in cool season grass vs warm season grass and how you should close out the season.
When Should You Stop Mowing Your Lawn Before Winter
The simple answer to when should you stop mowing your lawn for the season is, when it stops growing. For both cool season and warm season grass, this is usually when soil temperatures consistently dip below 55 degrees. To monitor soil temps you can check out Green Cast Online, or collect your own data by using a soil thermometer. You have to take the long term forecast into consideration though before putting your lawn mower away for the season. If you get a warm stretch of weather soil temps could increase and grass could put on new growth. Typically, your lawn will gradually slow down the later you get into fall, and you’ll se a long term forecast that will make you feel confident the lawn is getting ready to go to bed for the winter.
After the last mow, it’s a good time to put down your last application of fertilizer. This is usually referred to as winterizer and it’s important to know that winterizer fertilizer is very different for cool season grass and warm season grass as discussed here.
Last Mow of the Season Cool Season Grass
After the heat of the summer, your cool season lawn will be loving life in late summer/early fall. As soil temps hit the low 70’s to mid 60’s you’ll actually notice your cool season lawn enter into a bit of a growth spurt. During this time I recommend maintaining your regular height of cut. But once soil temps decrease to a point where your lawn is starting to slow down and you don’t have to mow as often, it’s a good time to start the gradual decrease in mowing height. Gradual is the key word here. Most mower decks have half inch intervals so only drop your deck by half an inch. Maintain that height of cut for several mowings. As soil temps continue to cool down to 55 degrees and you only have a couple of mowings, or maybe only one more mow left, you have some decisions to make. Do you mow an additional notch lower, or maintain your height of cut. This is where I say it depends on how high you’ve been mowing all year. Personally, I mow high, usually 4” all through the summer. My first drop of mowing height in early fall is to 3.5” and for the last mow or two I drop an additional half inch to close out the season at 3”. For cool season lawns, I would really make an effort to be at no more than 3” high for your last mow. If you’re wondering why, it’s because there are benefits to leaving your lawn on the short side over the winter months:
- When grass is long it can bend and flop over. Bent over grass, covered in snow, can create conditions that are likely to cause snow mold. Shorter grass is less likely to flop over when it snows.
- Voles, and other critters are more likely to tunnel along your grass if it is long and flopped over. The snow, and tall grass combine to offer them protection from the cold and from predators and you can be left with a lot of damage in early spring.
- Increased air flow from a shorter cut helps prevent fungus and disease.
Overall, your decision to mow lower than 3” is up to you. Dropping down to 2.5” or even 2” is great but only if you’ve been mowing relatively short all year and your lawn won’t look scalped afterwards. This is important to point out. You do not want to scalp your lawn for the last mow of the season. Your lawn gets used to its normal height of cut and cutting too short could cause you to cut into the crown of the grass. The crown is where carbohydrates are stored and used for energy in the winter and early spring. Cutting too low can cause damage to the crown and do way more harm than good. Instead of dwelling too much over mowing heights to close out the season, I really want you to consider how low can you go so that your lawn still looks nice and healthy, and not scalped afterwards. It should appear green, not brown when mowing for the last time of the season.
Last Mow of the Season Warm Season Grass
Unlike cool season grass which benefits from a gradual decrease in mowing height during the fall, your warm season grass may actually benefit from a slight increase in mowing height as fall progresses. The reason for this difference is the way dormancy occurs in cool season lawns vs warm season lawns. In cool season lawns there is complete dormancy meaning the grass blades as well as the root system go dormant. In warm season lawns the top portion of the lawn goes dormant, but the soil doesn’t freeze. This leaves the roots active throughout the winter. Because they are active, they are vulnerable to random periods of cold weather that can produce freezing temps, frost, ice, or snow. This is where mowing slightly taller during the fall can be beneficial. Studies have shown a connection between mowing height and root depth. Mowing slightly higher creates deep roots. Deeper roots will be more protected from winter weather conditions that can cause damage.
Of course, there are a lot of variabilities among those with warm season grass types. You could be in a climate so warm that your warm season grass doesn’t go dormant at all. If that’s the case then just maintain your normal mowing height throughout the winter months.
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