Winterkill: How to repair winter’s damage to your lawn

While you’ve stayed toasty in your warm house this winter, your lawn hasn’t had that comfy choice. It’s been out in the cold, perhaps getting damaged. Whether your winter was mild or polar vortexted, spring’s approach and the melting of the snow cover gives you a chance to see if you need to make lawn repairs.

Here are 3 steps the experts say you should take:

Step 1: Assess

First, take a deep breath. If your lawn has been through winter conditions in your climate before, and if it was healthy going into the winter, chances are it needs just a little TLC. It has just gone through a stressful period, but probably it only needs some light rejuvenating care — the gardening equivalent of hot cocoa after a day on the ski slopes.

People in northern climes generally plant cool-season plants, and they deal every year with winter damage. In the South, as you would expect, warm-season grasses dominate and winter damage is mild to nonexistent. In the transition zone in between, both types of grasses are planted. Transition zone people beware: If you planted a warm-season grass lawn and you had a severe winter, you could have more work on your hands.

Below are major types of grasses, and their cold tolerances.

See related story: “Grass Types: Which One Is Right for Your Lawn?“

When the snow and ice let up, get out there and have a look. A close look. You probably think of a lawn as a single entity, but remember that a lawn is composed of thousands of individual blades of grass. At the bottom of each grass plant, just above the ground, is the crown of the plant. All blades of grass emerge from a crown.

You are likely to see brown patches, but that’s OK. Get down and inspect closely to see if the crown is still whitish in color. If it is, that grass plant will recover.

“The homeowner is really going to have to determine: Is it brown because it’s dormant? Or is it brown because it’s dead?” said  University of Illinois Extension educator Richard Hentschel. “If the crown’s alive, the recovery is going to happen like it does every spring,”

He suggests rubbing a small area of the lawn vigorously. If grass plant crowns remain with at least a bit of green growth present after you have buffed away the brown bits, you are good.  If you end up with bare ground “chances are it’s dead,” Hentschel said. “For those grass plants, there’s no recovery.”

But if the crown has also turned brown and dried out, that grass plant likely has died. You’ve got “winterkill.”

What is winterkill? According to a paper by Dr. Kevin Frank, a Michigan State University turfgrass expert with a specialty in winter grass injuries, “Winterkill is a general term that is used to define turf loss during the winter. Winterkill can be caused by a combination of factors including crown hydration, desiccation, low temperatures, ice sheets and snow mold.”

Step 2: Identify your culprit

Let’s take a look at each possible source of winterkill:

Crown hydration

Let’s say you’ve had a few warm, late-winter days. Your grass thinks, “Ahh, warmth. Spring must be here. Time to soak up some water so I can start growing.” Wrong move.

Because lawns can’t watch the Weather Channel, they didn’t see the report that a late-winter hard freeze was blasting their way. When that late-winter freeze arrived, the water they took up froze into crystals inside the grass plants’ crowns, rupturing them and leading to its plant’s demise.

There’s little that can be done after the fact except to see how widespread it is so you know how big a repair job you have. Among common consumer landscapes, annual bluegrass is particularly susceptible to crown hydration issues.

“This phenomenon is related to a sudden change of weather when after very hot weather sudden frost occurs,” said Bryan Stoddard, director of Homewaresinsiders.com in New Jersey. “This is the most common occurrence in late winter or early spring, especially when morning frosts appear.”

Winter desiccation

Where crown hydration is too much water, winter desiccation is too little. If you have had a cold, dry winter, the crowns of grass pants can lose more water than they gain, and die.

According to University of Nebraska-Lincoln‘s turf and soil specialist and assistant professor Bill Kreuser, lawns of predominantly Kentucky bluegrass, fescues, or buffalograss are more tolerant of winter desiccation stress.

If a cold, dry winter is still underway, homeowners can protect their lawns by topdressing exposed areas and keeping traffic on them to a minimum.

Snow mold

Snow mold is the name given to a variety of molds that exist under the snow or wet leaves. They can cause a pinkish or grayish tint to the lawn, and may take on a web-like appearance. Snow mold dies off naturally, but if it is a persistent issue, spot applications of fungicide can prevent it from coming back.

If you have snow mold, your lawn may not be the only thing needing treatment. You might, too. Snow mold “releases its spores basically when the snow is melting and there are high humid condition, mold spores and fungi, which people can have allergies to,” Dr. Marty Trott, an Ear, Nose, & Throat Specialist at St. Johns Medical Center in Jackson Hole, Wyoming, told an interviewer.

Ice sheets

Because cold-season grasses are adapted to winter and go dormant, it takes a lengthy period of cold for ice sheets to kill them. James Beard, the late agronomist who wrote textbooks that are turfgrass industry standards, experimented on two common homeowner turfgrass varieties, Kentucky bluegrass and creeping bentgrass. Each survived 150 days under ice cover.  Beard concluded they were finally done in by a buildup of toxic gases under the ice.

Voles

Voles are small rodents that can do a lot of damage to your lawn. The North American vole ranges from Alaska across the northern U.S. and farther south along the Atlantic coast. As voles hide from their many predators, they like to burrow paths just under the snow. When that snow melts away, surprise! The homeowner finds a series of unsightly ruts or “runways” in the turf.

Voles leave a lot of excrement, too. But because voles only eat the blades of grass, and not the plant’s crown, grasses usually recover.

How to repair your lawn after voles have damaged it? Rake up the excrement and reseed. More extreme measures are usually not cost-effective: According to the University of Massachusetts-Amherst extension office, prime vole country can support about 300 of them per acre.

How to make your lawn less inviting to voles? Move woodpiles and other sources of cover away from the lawn, and give your lawn a shorter cut just before winter sets in.

Step 3: Repair winter’s damage

Repairing winter’s damage will depend on how extensive the damage is, and your local weather and soil conditions.

Here’s what to do if you think you’re dealing with winterkill:

Assess: Is the grass really dead?

First, you want to see whether those brown sections are dead or just dormant. Carefully dig out a few of the individual grass plants, bring them inside and see if they green up. If so, it’s just been hibernating and your lawn’s natural regenerative cycle will take care of things.

But substantial winterkill calls for a round of remedies.

Test your soil

Test your soil if you haven’t done so lately. There are home soil testing kits, some mail-away kits and professional soil testing services. The pros may have different levels of service — you pay more, they test for more things.

Before you reach for your credit card, though, check with your local agricultural extension service. Some of these government agencies provide low-cost or even free soil testing. 

At a minimum, your testing kit will test for your soil’s pH level to help you know whether your soil is acidic or alkaline. In general, turfgrass likes soil that is a bit on the acidic side.

Apply soil amendments as your soil test indicates.

Aerate

We think of soil compaction as something that happens in warm weather, but your lawn can suffer from compaction during winter, as well. Aerate your lawn, preferably with a core aerator, to loosen the soil if compaction is an issue.

Consider a pre-emergent herbicide

Pre-emergent herbicides will help your lawn along by preventing last fall’s weed seeds from germinating.

But pre really means pre. You want to get the weeds seeds before they germinate. The magic number is 55, according to the University of Missouri extension office. If the top inch of your soil is 55 degrees or more for five consecutive days, that’s when to apply. Follow label instructions carefully.

“Unfortunately, the recovery from winterkill seems to be following the common saying of slow and steady wins the race,” says Michigan State’s Frank.

Take these steps and your lawn will go from brown to green in plenty of time for your warm-weather activities.

When to Call a Lawn Care Pro

If you’re not sure how to help your lawn to go from brown to green again after winter, a LawnStarter pro near you can get your grass healthy again — and then handle all your mowing and other yard needs through the year.

Main Photo Credit: FelixMittermeier / Pixabay / License

Daniel Ray

Daniel Ray is LawnStarter.com's former editor in chief. He is an award-winning writer and editor who previously was editor in chief of the personal finance websites Bankrate.com and CreditCards.com, but with 30 years of gardening experience, he's well qualified to help consumers grow a different kind of green.

Posts by Daniel Ray