As Halloween approaches, the cold weather creeps in, and thoughts of putting the lawn to bed for the winter are afoot. I use this time to review my mental checklist of winterizing my yard and begin getting together all the tools and products I’ll need to get the job done. I have warm-season grasses, so I have to mow my grass low before daytime temperatures drop too far.
Whether you have cool-season grasses or not, you will need to get your lawn prepared for the winter months to prevent snow mold and other turf issues of the colder months. Knowing when to mow last before frozen grass or dormant turf sets in and how low to cut it will help make sure you still have a beautiful lawn in the spring. Read on for winter lawn care techniques for a healthy lawn.
When Is the Last Mow Before Winter?
As convenient as it would be, the last mow of the year is not on a certain day. Unlike daylight savings, you will not be told ahead of time when it’s the right day to cut the grass a final time. A good rule of thumb is to run your lawn mower the last time before daytime temperatures drop below 40-50 degrees regularly.
Cool-season grasses and northern grasses, such as Kentucky Blue Grass, tall fescue, and annual ryegrass, need to be cut low over the course of several weeks to get them to the ideal height to overwinter and this should be down when the weather is above 50-55 degrees. Warm-season grasses and southern grass species can be left the same height or even allowed to grow a bit, depending on the fall lawn mower height and the type of grass.
Most grass types need to be reduced to a lower grass height before the first frost of the year to prevent fungal diseases. You will need a sharp blade on your mower to avoid damaging grass blades as the temperature drops. Adjusting your mowing height and getting the turf the correct inches tall is not all you need to do to your lawn before winter. Other steps need to be taken to make sure your green grass survives the cold and snow.
How To Prepare Your Lawn For Winter
It’s common for autumn to leave us with messes in our yards in the form of leaf litter and yard debris. As chilly winter approaches, the last thing most of us want to do is yard work, but to avoid dead grass blades, improve growth rate, and stimulate root growth, you will need to winterize your lawn. For complete details on winter lawn preparation, check out the table below.
| Preparation | Purpose | Tips |
| Pick Up Sticks | Protect mower blades and avoid damage to grass | Use a strong-tined garden rake or lawn sweeper to collect sticks fast |
| Reduced Height of Blade per Mow | Get the lawn to its optimal grass height without damaging the grass before winter | The one-third rule advises that the mower only makes grass shorter by 1/3 of an inch per mow, regardless of grass type |
| Mulch Fallen Leaves | Added to the lawn for warmth, protection of beneficial insects, and lawn fertilizer | Mow the leaves several times throughout the fall and winter to reduce the likelihood of snow mold and to protect cool-season grass from deep snow |
| Dethatch Turf | Remove dead lawn materials, grass clippings, and other debris that will trap moisture and rot under the cover of snow | Cutting the entire lawn to the proper height will make it easier to collect the thatch and avoid the health problems lawn debris cause |
| Aerate Lawn | If you aerate the lawn before winter can bury grass under snow cover, then the moisture from snow will go into the ground instead of causing gray snow mold | Warm-season turfgrasses go dormant in the winter, and compacted lawns can lead to excessive fertilizer where winter weeds can access it |
| Fall Fertilizer | To prepare the roots of grass for winter and fall, fertilizers can be applied. The high potassium and slow-release nitrogen ensure a green lawn in spring | Use a combination of fall fertilizer and herbicides to make sure your turf gets what it needs and avoid a lawn at risk of weeds |
| Mow To Final Winter Blade Height | To get the entire lawn at the right height to survive cold weather conditions and excessive moisture | Cool-season grasses and warm-season lawns need to be cut to different heights based on what each grass lawn will endure in its climate |
1) Pick Up Sticks
Cool-season lawns often have a lot of lawn debris from the windy fall weather. To keep the lawn healthy and avoid damage to mower blades, you will want to remove all of the sticks. Big branches should be removed by hand, while smaller sticks can be raked or grabbed with a lawn sweeper. Twigs can be mowed over along with weeds and grass clippings.
2) Reduced Height of Blade per Mow
As the weather moves a lawn into dormancy, you will want to slowly reduce the height of your lawn grasses. Each time you mow for several weeks until your last mow, you will need to reduce the blade height on your mower by 1/3 of an inch. To know when to start dropping your blades, find the anticipated first frost date and work backward to find the correct day to drop the mower.
If you drop the mower more than 1/3 of an inch at a time, it can cause damage to grass blades, according to lawn care professionals. Most cool-season lawns need to reduce their lawn height by 2 inches or more, so it will take several weeks of mowing to achieve that. To avoid lawn issues, keep mowing at the proper lawn height until the temperature drops and your grass goes dormant or throughout the winter as your grass and climate dictate.
3) Mulch Fallen Leaves
As you are mowing your lawn and reducing taller grass, it is practical to also mulch the fallen leaves. Mulch adds many benefits to a lawn and contributes to healthier grass overall. leaf mulch can build fertilizer, protect beneficial organisms from heavy snow and extreme weather conditions, and can prevent frozen turf and brittle blades from weakening your lawn. Leaf litter has also been shown to suppress weed seeds germinating in the spring, helping to give your turf a fresh start when the temperatures rise.
Too much of anything can cause an issue, and often more leaves drop from our trees than our grass needs. Cooler weather and a deep layer of leaf litter can cause poor growth and cold weather damage. Surplus leaf litter from the lawn can be used as mulch under trees to keep their roots warm during the harshest winter months.
4) Dethatch Turf
Some warm-season grasses and matted grass blades can become full of old grass clippings and yard debris. These organic materials rot rather than break down and can cause anaerobic conditions. Under a layer of snow, gray snow mold can grow and increase your turf’s disease issues, plus bring pests and weeds to your lawn. Rake and compost or use the thatch as mulch under trees.
Once the decaying yard waste has been removed, there will be less environmental stress on your turf and a better chance of withstanding extreme winter temperatures. Each type of grass will need to be dethatched differently as some can become severely damaged if done incorrectly, requiring an expressive resowing of the entire turf.
5) Aerate Lawn
Healthy grass needs water and fertilization, and it has to be able to get oxygen to its roots. Aeration is the best way to make sure that happens. It is important to cut the grass short and remove yard debris to improve the effects of aerators. A lawn with plenty of air holes and reduced compaction will hold up to a layer of snow better than a lawn unprepared for winter weather.
6) Fall Fertilizer
Even though most types of grass go dormant in the winter throughout fall and early in spring, there may be active growth. For a lush lawn, give your turf the essential nutrients they need. Avoid giving too much nitrogen in the fall, or else you may need to mow your grass on warmer winter days to prevent frost damage when it turns cold again.
7) Mow to Final Winter Blade Height
The exact height you will want your lawn to be before winter depends on the type of grass you have. In general, winter grasses will need to be cut lower than summer grasses as they can continue to grow on warmer winter days. When the right height is reached, you can allow the grass to go dormant and only perform small lawn trims when needed.
What Is the Shortest Height Grass can Be Mowed Before Winter?
A good rule of thumb for the ideal lawn height is between 2 to 2.5 inches high. According to Michigan State University, cool-season grasses should be cut and maintained at around 1-2 inches. At 1-1 ½ inches, there can be a risk for disease if conditions are wet and the snow cover is heavy.
Warm-season lawns can be cut to about 2.5-3 inches and survive the dormant months with no issues. If your grass was lower than 3 inches in the summer, you can allow it an inch increase to protect the root from the cold winter temperatures. In this case, increase the blade per mow by 1/3 of an inch until it is the correct uniform height to weather the winter.
Is It Okay to Mow After a Frost?
Once the frost has hit, the leaf blades on grass turf become fragile. Cool-season grasses can usually handle mowing on warm days in the winter, whereas perennial warm-season grass can be severely damaged if mowed while dormant. Cool-season grass shouldn’t be mowed during a frost as it will dull the mower blades and harm the turf.
It is always best to cut taller grass down to the right height before the winter season arrives. Grass that is too tall can lead to mold issues and other risks for disease and reduced plant health. Start reducing your grass height in the late fall and resume cutting when the temperatures have warmed up, and your spring turf is experiencing consistent growth. Remember to weed your yard when the garden soil warms up to eliminate broadleaf seeds and other weeds seeds from taking over your turf.