If a frost occurs within 1–2 days after cutting your grass it can cause damage to the grass blades. Grass growth halts in cold temperatures, so freshly cut blades of grass cannot recover from the stress of mowing. The cold and moisture brought on by a frost can weaken your grass, cause yellowing/browning, and an increased chance of grass disease.
Ideally, you should mow for the final time 1–2 weeks before the first average fall frost. In spring, wait 1–2 weeks after the last average spring frost to resume mowing.
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Does Frost Damage Fresh Cut Grass?
Even a light frost can damage freshly cut grass. Grass that has been newly cut essentially has an open wound where the grass blade has been sliced. In warmer temperatures, grass can easily repair this damage because it is actively growing. When temperatures dip toward freezing, grass stops growing and does not repair itself after mowing. The following harmful effects can be caused by a frost after mowing:
- Browning/yellowing grass
- Patches of dead grass
- Grass rot or fungus
- Poor green-up in spring
Weakened grass exposed to cold weather can experience a number of setbacks. Do not mow grass during cold months.
Avoid Winter Mowing with Frost
Because mowing grass when frost is in the forecast is damaging to turf grasses, follow these rules to keep your grass safe during the winter months.
- Check the first and last frost dates for your region.
- Mow grass the right height for last time in fall 1–2 weeks before the first frost date.
- Mow for the first time in spring 1–2 weeks after the last frost date.
- Do not mow when daytime temperatures are below 40 degrees Fahrenheit.
These simple guidelines will ensure that you mow grass only when it is safe to do so. It will protect your lawn from frost damage.
When Should You Not Cut Your Grass?
Avoid mowing when temperatures are near freezing. Mowing frozen or frosted grass can cause extreme damage, destroying grass blades, and killing grass down to the roots. Most lawn care experts advise you to stay off your lawn completely when frost is present. Even walking on frosted grass can break and damage grasses.
Do not mow if any of the following is true:
- Air temperature is below 40 degrees Fahrenheit.
- Frost, ice, or snow is present.
- Grass is wet.
- Grass is dormant (brown, not actively growing).
If temperatures are near freezing, the best course of action is to leave the lawn mower in the garage. It’s better to let your grass remain a little long through the cold months than risk causing damage by mowing frozen or wet grass.
How to Help Cut Grass Recover from Frost Damage
If your grass has been damaged by frost that arrived shortly after mowing, the best course of action is to remain patient. The worst of the damage won’t be visible until spring. Do not mow your lawn again, stay off of frozen grass as much as possible, and wait until conditions improve.
In spring, plan to fertilize your lawn with a high-nitrogen fertilizer to jumpstart blade growth and feed grass roots. Most turf grass species will benefit from a spring application of fertilizer, but frost-damaged grass needs it more than ever.
Wait until the grass begins growing thickly again and is 4 inches in height to resume mowing. It’s essential to wait until freezing temperatures are in the rearview mirror to resume mowing, to prevent further frost damage.
Is it OK to Cut Grass Before a Frost?
Frost forms when temperatures dip below freezing. Unlike ice, frost does not require standing water to form. The ice crystals in frost come from water vapor in the air, so dry grass is as likely to be covered in frost as wet grass.
Frost damages freshly cut grass because it brings moisture (in the form of that frozen water vapor) in contact with fresh-cut grass. Disease and rot caused by moisture can infiltrate freshly cut blades of grass when temperatures are too cold for the grass to grow and heal. This makes the winter months the worst time to mow your lawn.
Do not mow grass if freezing temperatures are in the forecast within the next 3 days. Ideally, you should mow at least 1 week before the first fall frost and 1 week after the last spring frost. This will protect your grass from harm.