Here's What a Late Spring Freeze Does to Your Lawn
It seems to happen every year if you live in that transition zone that extends from the Mid-Atlantic down into the South. March arrives, temperatures warm up, and your lawn begins to awaken and grow. Then, seemingly without warning, a cold snap hits, dropping temperatures back down into sub freezing territory. This can spell disaster for plants, which can see buds whither and turn brown. You can cover shrubs to protect their flowers. But there’s not much you can do for your lawn, leaving you to wonder how your green grass will handle a late hard frost.
Related: Hard Freeze to Hit the Mid-Atlantic and South—Protect Spring Blooms
A Tale of Two Grass Types
How your grass fares in sub freezing temperatures after it has already come out of dormancy depends on whether you have a cool season or warm season grass type, both of which are common in that transition zone that extends from Virginia down into Georgia.
Warm Season Grasses
Warm season grasses face the most potential damage. If weather has reached into the 70s for an extended period, chances are that warm season grass has already started waking up. If so, here’s what can happen when temperatures suddenly plummet. When temperatures drop into the mid 20s, warm season grasses that began to turn green when weather was warmer can suddenly turn brown or even gray overnight as water inside the plant freezes and ruptures its cell walls.
Don’t panic. Warm season grass is very resilient. The cold may have damaged the crown of the grass, the part that’s just below the soil line, but it will recover. While your Bermuda or zoysia grass may look brown for a couple of weeks, it should begin greening up again when the weather warms.
There is an exception here. Since St. Augustine grass has above ground stolons, it can suffer permanent damage if temperatures stay under 25°F for more than a few hours.
Cool Season Grasses
Cool season grasses are built to handle cold weather, so your lawn should be safe even with prolonged sub freezing temperatures. There is a caveat here. If you planted new grass and it started sprouting during that stint of warm weather, it may not survive a hard freeze, which may mean you’ll need to reseed as soon as temperatures warm up.
The Danger of a Late Season Frost
While an early spring frost may not cause permanent damage to your lawn, it can if you’re not careful. There’s certain restrictions you need to put in place when temperatures drop back below zero to protect your lawn:
Ban Foot Traffic
Avoid walking on frozen grass. When the grass freezes, ice forms on the blades. If you walk on the grass, those ice crystals can cut into the cell walls of the grass blades, causing damage. You’ll be able to tell if you've damaged your lawn if brown footprints appear on your lawn a few days after walking on it. Stay off the grass until the ice has completely melted.
Related: Stop Walking on Your Lawn When It’s Frozen—Here’s Why
Delay Fertilizing
Your first instinct may be to fertilize the grass to help it recover. Resist the urge. While it may seem logical to feed your grass, doing so promotes new growth, setting it up for further damage if another frost hits. Hold off on fertilizing your lawn until you are absolutely sure the threat of frost has passed for the season.
Hold Off On Mowing
While your grass may have grown to a mowable height in that warmer weather, now is not the time to cut it. Give your grass 4 or 5 days to recover from the frost before subjecting it to the stress of its first mow of the year.
How to Prevent Late Season Freeze Damage
Your lawn may be far too large to cover to shield it from frost, but there is something you can do. A couple of days before the hard freeze, give your lawn a good deep watering. Moist soil retains heat longer than dry soil, so it acts as insulation for grass roots, helping to protect them against freezing temperatures. Only water when temperatures are above 40°F.