If you live in colder regions of the U.S., you’ve probably experienced winterkill. Winterkill is when harsh winter weather kills or damages grass and plants, often leaving behind a patchy mess come springtime.
Freezing temperatures, harsh winds, layers of ice, or even sudden shifts in temperature can all lead to various types of winter damage, including desiccation, crown hydration, and snow mold. Those conditions stress the grass, potentially killing it.
Signs of winterkill
When you walk outside for the first time after a long winter and take a good look at your lawn, you might notice areas where the grass isn’t looking as healthy as it should.
Winterkill manifests itself in a few ways, including:
- Discoloration of grass blades: Grass can turn yellow, brown, or gray.
- Shriveled grass: The grass may seem dry and lifeless. This is called desiccation.
- Bare patches: Dead zones in your lawn where grass doesn’t grow back.
- Matted grass: Grass flattens down, preventing water and sunlight from reaching the roots.
- Circular patches of snow mold: Matted areas that are dirty white, gray, or pinkish brown indicate snow mold fungus.
- Thin or patchy lawn areas: Broad sections of your yard might appear noticeably dead.
- Delayed green-up: In spring, spots fail to revive while the other parts of your lawn get greener.
Causes of winterkill
Think about all the things your lawn goes through during winter. The freezing cold, heavy snowfall, icy rain and wind – these are all pretty challenging conditions that can spell trouble for your grass.
Here are the main reasons for winterkill:
- Crown hydration
This is when grass sips up water during a brief warm spell in the winter, and then temperatures drop fast. The water freezes quickly and expands inside the grass cells, which kills the grass.
Peter Landschoot, Ph.D., a former professor of Turfgrass Science, explains, “Crown hydration is the most common and destructive type of abiotic winter injury and usually occurs in late winter following periods of thawing and freezing.” It generally occurs during late winter, like February and March.
*Note: Annual bluegrass and perennial ryegrass are especially sensitive to crown hydration, making these grass types more prone to winterkill damage.
- Winter desiccation
Winter desiccation happens when grass is whisked by cold winds without the protective blanket of snow. This persisting chill can dry out “crown tissues,” where new plant growth takes root, making lawns vulnerable to death.
*Note: Purdue Turf Program experts point out that areas with dry soil or minimal snow cover are more at risk of winterkill desiccation. This risk is particularly common in drier states such as Kansas, Nebraska, the Dakotas, Wyoming, and Montana.
Pro tip: Combating winter desiccation requires proactive steps like sprinkling sand topdressing in late fall or using fabric covers and windscreens around vulnerable areas.
- Snow mold
Snow mold, the lawn-damaging fungus that attacks cold-season grasses in winter, comes in two forms: gray snow mold, which lives under lengthy snow cover, and pink snow mold, which can happen with or without a snowy blanket. This condition can eventually starve the grass for air and sunlight, leaving unsightly patches.
Pro tip: If you’re continuously tackling this issue every winter, a preventive fungicide application in the fall could be your best line of defense.
Check out our complete guides:
- “What is Gray Snow Mold and How Do You Get Rid of It?”
- “What is Pink Snow Mold and How Do You Get Rid of It?”
- Ice sheets
Ice sheets often form over lawns when rain or melting snow quickly freezes. These sheets suffocate the grass underneath, blocking oxygen and holding harmful gases close to the ground. With prolonged exposure, your lawn can suffer extensive damage.
*Note: Aaron Patton and Cale Bigelow, from the Purdue Turf Program, detail how ice accumulation poses a significant threat to the turf. Essentially, when annual bluegrass is under ice for 45 to 90 days or creeping bentgrass for 90 to 120 days, it can die due to hindered gas exchange and increased carbon dioxide levels.
- Low-temperature kill
Low-temperature kill occurs when grass hasn’t had time to prepare for winter. Normally, grass slowly removes water from its cells during fall to protect against freezing temperatures.
But when fall stays unusually warm, the grass keeps growing instead of preparing. If temperatures suddenly drop well below freezing, the unprepared grass can die, especially without protective snow cover.
How do you know your lawn is really dead?
Spotting dead grass isn’t always straightforward. Signs like discoloration and patchy growth are certainly clues, but they don’t always provide a definite answer.
To know if your lawn suffered winterkill damage, try a simple pull test. All you need to do is grab a handful of grass and give it a steady tug. If your turf pulls up easily with no resistance – just like lifting a carpet – it indicates significant winterkill damage. Dead grassroots are weakly attached to the dirt, making it easy for them to pull away from the ground.
Why it’s important to repair winterkill
Once spring arrives, you should address winterkill promptly. Besides the obvious reason of woeful aesthetics, here are some key reasons why addressing winterkill is important:
- Prevents weed growth: Dead patches attract plant invaders looking to claim valuable open space. If left untreated, weeds will sprout and choke out any surviving grass.
- Defends against pests: Damaged lawns can also provide an ideal home for harmful pests like grubs and beetles who love munching on struggling roots.
- Increases property value: A well-maintained lawn lifts your entire property’s appeal and resale potential.
- Nips problems early: Early intervention restricts widespread damage, saving you more extensive repairs later on.
FAQ about winterkill
How to prevent winterkill?
While not entirely preventable, proper lawn care throughout the year can minimize winterkill damage. Take steps in the fall, such as:
- Aerate your lawn;
- Apply winter fertilizer;
- Perform your last mow of the season;
- Clear lawn of debris;
- Keep foot traffic minimal.
Also, prevent winterkill by overseeding your lawn with resistant grasses like Kentucky bluegrass and rough bluegrass in the fall (late August to early September). Avoid or use less of Perennial ryegrass and common Bermudagrass; they’re more likely to suffer from extreme cold.
Check out our complete guide on “How to Winterize Your Lawn”
Are there areas more prone to winterkill in lawns?
Certain areas are more prone to experiencing winterkill. These include:
- Areas lacking proper drainage: When lawns have inadequate drainage, water tends to build up and freeze, causing damage.
- Areas frequented by foot traffic: Walking on frozen grass can break the blades and eventually cause them to die off.
- Sections with poor nutrition or shade: A lack of necessary nutrients or sunlight makes these areas more vulnerable.
How do you repair winterkill in your lawn?
Restoring winter-damaged lawn begins with raking away dead grass. Then, aerate and overseed the affected areas while nourishing them with a balanced fertilizer to encourage regrowth. Ensure regular watering until new sprouts mature. (Here is our complete guide on “How to Bring Grass Back to Life”)
Hire a lawn care professional
Sometimes, winter damage to your lawn is hard to prevent. If you don’t know where to start, bring in a pro. Lawn Love connects you with top local lawn care professionals who can restore life to your faded yard this spring.
Main Image Credit: maykal | Adobe Stock Free | License
