What Temperature Does Grass Stop Growing?

Maintaining a lush, green lawn is one of the primary preoccupations of most homeowners. However, in most parts of North America it’s not possible to keep grass growing year-round. At both ends of the temperature range, you can expect your grass to stop growing.

Grass will stop growing when the air temperature falls below 40-50°F (4.5-10°C), and also when temperatures stay above 90°F (32°C). Knowing this important information can prevent you from panicking when your lawn starts to go into its dormant phase and turns brown.

Does Grass Stop Growing in the Winter?

Grass plants will stop growing when temperatures drop below 40-50°F (4.5-10°C). While the blades will not grow any taller and in fact will turn brown as temperatures continue to drop, they focus their energies on withstanding freezing temperatures. This ensures the survival of the crown over the winter, which will put forth fresh growth when spring arrives.

Will Grass Grow During a Freeze?

Grass will not grow in freezing temperatures. Instead of wasting their energies on growing blades, the plants concentrate on maintaining strong root systems and healthy crowns to survive the cold winter.

Will Grass Grow Underneath Snow and Ice?

Grass will not grow upward when covered with snow and ice, but a blanket of snow is one of the best things that can happen to your lawn in cold winter temperatures. Snow is an excellent insulator and will protect your grass from extremely cold weather.

As well, some sunlight will make it through the snow and ice and the resulting photosynthesis fuels the development of healthy roots. That will make your lawn grow even better the following spring and summer.

However, walking on a lawn covered with snow or ice can cause damage to the grass plants. Try to stick to paved paths to protect it.

Will Grass Seed Germinate in Cold Temperatures?

Grass seed will not germinate in temperatures below 50°F (10°C). The best time to seed a lawn is in early fall, so that it will have time to sprout and get established before freezing temperatures arrive.

It is also possible to spread seed shortly before the ground freezes. This is called dormant seeding. The seeds will then sprout as soon as warmer temperatures arrive in spring, getting them off to an early start.

However, if you cannot count on reliable snow cover to protect the seeds from getting washed away or eaten by animals or birds, it’s best to wait until early spring to sow your grass seed.

Do All Grass Types Stop Growing in Winter

Do All Grass Types Stop Growing in Winter?

Depending on your location, you may be able to have a green winter lawn. In the cooler parts of the sunbelt of the United States, warm-season grasses such as St Augustine grass or Zoysia grass will go dormant and turn brown as temperatures drop, but cool-season grasses such as annual rye grass will thrive in a southern winter.

When average temperatures fall to around 70°F (21°C), generously overseed your lawn with annual rye grass seed. It will quickly germinate and keep your lawn looking green all winter before dying when the hot weather returns in spring and the perennial grasses spring back to life.

However, in regions with freezing temperatures, you don’t have any options for keeping your lawn growing in winter.

Does Grass Stop Growing in Hot Temperatures?

Hot temperatures can also halt the growth of your grass.

While warm-season grasses like Bermuda grass can thrive in temperatures as high as 100°F (38°C), they will not survive freezing winters in northern regions. The cool-season grasses grown in those zones will not tolerate daytime highs above 90°F (32°C), and can become dormant until cooler weather returns.

While temperatures remain that high, the grass plants will not produce fresh blades, and the existing growth will turn brown.

Does Grass Need Water to Grow in Hot Temperatures?

The best way to prevent your lawn from becoming dormant during a hot spell in summer is by watering it regularly to lower the soil temperature.

Frequent light watering is not recommended. It’s best to wait until the soil has dried out, and then water the soil to the depth of the roots. Lawns only need an inch of water per week, and don’t water at all if there has been adequate rainfall.

You should water early in the day before the air temperature rises too high. This prevents the loss of water to evaporation, and helps lock in cooler temperatures in the soil.

Watering during the heat of the day can scorch the grass, so that is not recommended.

Do not water in the evening, as that can encourage the spread of disease.

Should You Keep Grass Long During Hot Temperatures?

During really hot weather, you should still mow your lawn, but set the mower blade higher than when it’s cooler.

When the grass is allowed to grow longer, it actually encourages roots to go deeper to find whatever moisture is in the soil, as it increases the leaf surface available for photosynthesis. The longer shoots also provide more shade for the soil, keeping it cooler.

The optimal length for grass in extremely hot weather is between 3-4 in (7.5-10cm). Never remove more than 1/3 of the height when cutting the grass, as that will place too much stress on plants that are already stressed by the heat.

The best time to cut your lawn is in the early evening, when the grass is dry after the heat of the day and before the dew falls. This will give the plants the cool evening to recover from the shock of being cut back before things heat up the next day.

If you have a mulching mower, leaving the clippings on the lawn will help keep the soil cool and return nutrients to the grass roots. Aside from that, do not feed the lawn, as you do not want to encourage too much growth when the plants are stressed by the heat.

Final Thoughts

While it might be nice to have a constantly green lawn, grass plants are living things that need to rest. Understanding their natural cycles can help you keep your lawn as healthy as possible, and minimize their periods of dormancy.

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