While grass shows up almost everywhere, and it often feels like something we can rely on to provide us with greenery through the seasons, the temperature does limit its growth. In fact, in colder weather, grass goes dormant and hardly grows, if at all.
Understanding when the grass stops growing and making sure you provide it with a last cut of the season can make the difference between a lawn that sees you good through the winter months as well as bouncing back to life the following springtime and one that looks waterlogged, patchy and in need of some serious TLC.
I know what you’re thinking. How can I keep my grass thriving after winter? Well, on top of weed control and nutrition, timing plays a vital role in crafting a beautiful lawn. I’m here to help you make a pre-winter plan so you know just when to mow your grass for the last time before the cooler weather hits.
When Does Grass Stop Growing
Grass stops growing when it faces temperature extremes. If you live in or near northern regions, chances are, your grass will stop growing around October when temperatures begin to drop. Grass in more southerly regions may continue to grow until much further into the year, maybe even into December.
Grass needs a few things to grow: light, warmth, water, air, and nutrients. Any deficiencies in these areas will typically cause the grass to stop growing and go dormant. While dormant and therefore preserving energy, the grass is able to protect itself from extreme temperatures and harsh weather conditions.
Soil temperature is a critical part of grass growth. The amount of heat in the soil can be affected by sunlight, solar radiation, cloud coverage, air temperature, grass coverage, the gradient of the land, fertilizer, rainfall, nearby bodies of water, and soil composition.
When temperatures drop, the microorganisms inside the soil struggle to decompose plants. The soil will release less carbon dioxide, hindering the photosynthesis of grass. Also, cold temperatures inhibit nutrient and water uptake from grass. This in turn will prevent roots from growing during this time.
Keep in mind that extreme heat can also cause many types of grass to go dormant. I know folks in Southern California who can’t keep their lawn green in the summer due to the heat and drought.
Grass responds to extreme temperatures by decreasing its active growth rate. This is not to say that the grass is dead and despite the dry and brown look of the blades, the grass will stay alive as long as the crown is protected.
Any water and nutrients that the grass receives go towards keeping the crown alive, not the blades. Grass blades are not a vital part of the plant, and they are the first to go when the grass enters survival mode.
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What Temperature Does Grass Stop Growing
The precise temperature at which grass stops growing depends on the species, but you can use this rule of thumb for most types.
Grass generally stops growing in fall or winter when the peak daytime temperature drops below 50°F.
Warm-season grasses often grow between 80-95°F. Some species, like the Zoysia grass and Bermuda grass, can range from 64-110°F. These varieties of grass may stop growing at slightly higher temperatures than the above rule, such as 55°F.
Cool-season grasses prosper between 50-65°F. These grasses will struggle to survive at temperatures above 85°F. Some winter grasses can withstand temperatures well below 50°F, but the most common species have poor tolerance to freezing.
When temperatures reach inhospitable ranges, the roots get damaged and stop growing, sending the grass into its dormant phase. The grass can no longer withstand cold atmospheric temperatures, so it relies on the soil’s warmth.
Generally, the soil temperature affects the grass in three ways:
- Growth – The soil temperature affects the speed of development. Usually, warmer soil temperature has more energy which stimulates a faster growth rate. Increased soil temperature enhances root growth because of the increased metabolic activity of root cells.
- Lawn Diseases/Damages – Your lawn has a higher risk of becoming infected with fungi during colder temperatures. If you see signs of fungal diseases in late fall, it’s essential to apply fungicide immediately before the grass goes into a dormant state.
- Germination – When reseeding your lawn remember that germination won’t occur unless you planted the seed at the correct soil temperature. Temperature and moisture are two essential factors in germination.
When to Stop Mowing Lawn in Fall
It is time to stop mowing your lawn when the grass goes dormant. At that point, you will only be cutting dead blades, which may put the crown at risk. Consider these factors to know when your grass is going dormant:
- Soil Temperature – Make sure you track the soil temperature. Look at a soil temperature map for your area and compare it to the temperature limits of your type of grass. You should stop mowing your lawn once the temperature goes below 50°F or your grass’s lower bound temperature.
- Length – Grass growth will slow drastically before dormancy. I find that when I stop having to mow my lawn every two weeks, it’s about to go dormant. If you no longer have to cut your grass regularly, you should stop.
- Frost – After a hard frost, many grass varieties will go dormant. If you’ve had a frost recently, you should stop mowing your lawn to protect the crowns, even if you have freeze-tolerant winter grass.
How Short To Cut Grass Before Winter
When preparing your lawn for winter, start cutting it to a two-inch length. If you normally cut it much longer than that, you can work your way down once summer fades away until you can comfortably cut it to two inches tall.
By keeping your grass to a two-inch height you can help to:
- Prevent Fungal Diseases — During winter, long grass is more likely to be affected by fungal diseases like snow mold. In fact, snow mold is one of the most serious diseases of turfgrasses in Alaska and other regions.
- Get Rid of Voles – Voles are small rodents and are considered turf pests. Long grass is a favorite of voles as it gives them food and protection from predators. Now, voles feed on healthy grass and roots, which leads to dieback and death. If there’s no snow cover, they’re less likely to stay in short grass because it won’t protect them.
- Reduce Winter’s Adverse Effects – Long grass usually experiences winter kill because the snow causes the blades to fold, leading to rot and disease.
Typically, you’ll want to perform your last mow when you see that soil temperatures have gone below the ideal range.
Mow Lawn Long or Short for Winter?
To prepare for winter, you should mow your lawn short. Try to go to a two-inch height so that the length can continue to photosynthesize before getting covered with snow. If you cut it too long, the frost will likely cling to the blades after a snowfall.
Here are some more tips to prepare your lawn for winter:
- Consider aerating during the fall and spring seasons when the grass is actively growing. Aeration increases water penetration, nutrient availability, and soil air exchange.
- Clear leaves from the lawn. Leaving the leaves lying on the lawn increases the risk of mold. It also blocks the air supply, which can cause the grass to rot.
- Fill in any bald patches with seed during the growing season to minimize any permanent damage from winter dormancy.
- Use pre-emergent herbicides. Most weeds actively sprout during spring and fall. Applying pre-emergent herbicides will mitigate weed growth in the colder months to help your lawn grow back beautifully.
- Change the direction of mowing each time you cut your lawn to avoid scalping the grass and compacting the soil.
- Use a good quality lawn fertilizer and fertilize regularly but especially during the fall season. I find that liquid feeds not only keep my grass green & healthy but also add nutrients to the soil that may have become depleted during the growing season.
Once winter ends, you should let your grass grow long again. Keeping your blades three inches or longer can prevent the growth and spread of weeds. Furthermore, tall grass indicates longer roots that can withstand harsh conditions and absorb nutrients better. Maintaining the health of your grass throughout the year will help it survive during the winter.
The only advantage to shorter grass is that it allows sunlight to warm the soil, which helps the microorganisms and plants with their functioning. Warm soil also contributes to faster growth and green-up of the grass. Unfortunately, it can also facilitate weed growth.
Do Any Grasses Grow During Winter?
Cool-season grasses have better luck growing in winter than warm-season ones. Some popular types of winter grasses include:
- Velvet Bentgrass
- Improved Tall Fescue
- Creeping Bentgrass
- Annual Meadow Grass
- Kentucky Bluegrass
- Prostrate Meadow
- Perennial Ryegrass
- Browntop Bentgrass
- Chewings Red Fescue
- Rough Meadow Grass
Most winter grasses are shade-tolerant, prosper in cold weather conditions, and can withstand harsh weather.
You will need to compare the growing conditions for these grasses to your climate before making a decision. If your yard can’t provide the necessary water, sunlight, air, soil, and temperature, the grass will not spread.
The tricky part of growing winter grass is finding the right time for planting. You have to sow the seeds while the temperature is warm enough for the seeds to sprout. If you plant too late, there won’t be enough time to establish the plants to withstand the freezing temperature.
When Does Grass Start Growing in Spring
When spring rolls around, your grass should start growing again once soil conditions become favorable for its species. Generally, that means when temperatures rise above 50°F. Since 50°F is low for most species, the growth will not be speedy at this time. Also, the precise temperature will vary for warm-season and cool-season grasses.
Warm-season grasses, typically found in USDA hardiness zones 7-10, start growing rapidly when the soil temperature climbs above 70°F. The warm temperatures and seasonal rains keep the soil hydrated and facilitate growth.
On the other hand, the cool-season grasses found in USDA hardiness zones 5-9 start to absorb moisture and nutrients at a lower temperature. They will grow rapidly when the soil reaches 55-65°F. With increasing daylight and enough water, the cool-season grasses flourish with deep-green hues if this temperature range remains constant.
First Mow of the Season
Once your grass begins growing rapidly, you might feel tempted to grab your lawnmower and hack away. I made that mistake once and had to plant more grass to get it to look nice again.
If you mow too soon before the grass thickens up, you expose the ground and weed seeds to direct sunlight. While this exposure will warm the soil and help with grass growth, it also contributes to weed growth. However, you can prevent this with pre-emergent herbicides. If that doesn’t get applied prior to winter, you will need to wait a little longer to start mowing.
For the most part, you do not have to mow before late March or ideally mow just before you weed and feed for the first time. In the weeks leading up to spring, you can remove winter debris, weeds, and matted grasses while leaving some grass blades to shade the soil and weed seeds. Try to let the blades get to around 4.5 inches before cutting to around three inches.
While you wait to mow, check the sharpness of your mower blades. Dull blades can make plants more susceptible to disease by leaving jagged edges. Cutting them cleanly can also conserve water.
When you mow, leave the clippings on the lawn. As the clippings decompose, they act as fertilizer and restore some of the nutrients the grass took from the soil. What’s more, they minimize runoff and increase carbon sequestration. Otherwise, you can mulch them if they are too long.
So, When Does Grass Stop Growing?
Your grass will likely stop growing around late October to early November if you live in a colder state and sometime in December in warmer regions. These months correspond to soil temperatures dropping below 50°F.
Having a mowing plan is the secret to a great-looking lawn. Be a master of your own backyard, and put everything you learn into practice to maintain a high-quality lawn all year round.