Frost on grass in front yard.

Treating Grass After a Frost

The first frost of the year has come and gone. Yet, temperatures continue to fluctuate as we head into the winter months. 

Depending on where you live in the Midwest, local temperatures can jump to 50°F (or above) in the daytime and fall below 32°F at night, causing frost to appear on your lawn during the fall season.

Like most homeowners, you’ve probably shelved your lawn equipment for the remainder of the year. But remember that frost on grass doesn’t mean your lawn has become dormant. 

In Minnesota, for example, grass will usually become dormant between late October and early December—once the soil drops below 50°F. So if your lawn still holds a green vibrancy and has not transitioned to a brown color—this is a good indication that it’s alive and growing. 

So what exactly is a frost? And how does it affect your lawn?

This article will address a few commonly asked questions about frost, so you know when and how to treat your lawn before winter.

What Causes Frost on Grass?

First, let’s cover what we mean by “frost.” Frost occurs when the water condensation on grass blades freezes overnight. For this to happen, temperatures need to dip below 32° F. If temperatures do not fall below freezing, dew will appear instead.

Light vs. Hard Frost: What’s the Difference?

A light frost occurs when the temperature at night falls to 32°F or below. During a hard freeze, the air temperature falls below 28°F for at least 4 consecutive hours.

A light frost is considered less severe than a hard frost since it won’t cause the soil to freeze, which can damage your grass’ root system. However, a hard frost makes it difficult for the roots to irrigate water and circulate its nutrients, eventually forcing grass to become dormant.

Does Grass Stop Growing after the First Frost?

Not quite. Frost is a good indicator that your lawn will eventually stop growing over the next few weeks. Once frost occurs regularly, the growing process begins to slow down and your grass prepares itself for survival during the cold winter months. 

Eventually, germination will stop entirely after the grass can no longer receive nutrients.

Can You Mow Grass after the First Frost?

Cool-season grasses can keep growing depending on your soil’s temperature. As a result, your grass may still need mowing. Remember that before you mow, you must thoroughly ensure the grass is thawed and dried. You never want to cut a lawn covered in frost. 

Ideally, if you decide to mow your lawn, you’ll want the temperature above 40°F. Be sure to also check future weather forecasts to ensure you have a few days before the next frost occurs as frost can damage your newly cut grass. 

Finally, avoid walking on your lawn after a frost, as this can also damage its blades.

Will Frost Kill Grass Seed?

Although new grass seeds can endure frost and will begin to germinate during the next growing season, it needs about 6-weeks to establish to overwinter successfully. 

Dormant seeding is a planting method that ensures the seed remains “dormant” due to the cold soil conditions. To get started, you’ll want to put down your seed while the ground is cold but not frozen. This ensures that germination of the grass seed will not occur until the following spring. In addition, sowing grass species that germinate more quickly and like cooler temperatures for germination is a good strategy for dormant seeding, in which fine fescues are a good option.

To learn more about dormant seeding and best practices, read this article from the University of Minnesota Extension

Is Your Lawn Ready for Winter?

Stay connected to our blog for more tips on caring for a lawn during the winter—and every season. And if you’re looking to get into the books for spring lawn care and landscaping in 2023, connect with our team today! 

We look forward to helping you plan and achieve your organic lawn care goals in the New Year!