LAWN GUIDE • BISMARCK, ND
Snow Mold and Vole Damage in Bismarck Lawns
If you see matted, straw-colored or grayish patches after the snow melts, that’s usually snow mold. If you see narrow, winding trails of dead grass running across the lawn, that’s vole damage. Both are common in Bismarck after a long winter under snow, and both usually recover.
The fix for each is simple: rake gently once the lawn dries out, then reseed any spots that stay bare. The better move is prevention, and most of it happens in fall, which is right now.
IDENTIFY THE PATTERN • MATTED PATCHES OR TRAILS
Snow Mold or Vole Damage? How to Tell
| What you see | Snow mold | Vole damage |
|---|---|---|
| Shape | Round patches | Narrow, winding trails that cross each other |
| Size | Pink: usually under 8 inches. Gray: 1 to 3 feet across | Trails about as wide as a vole, plus some larger dead patches |
| Color | Straw-colored, gray or pinkish, matted down | Brown strips of dead, eaten-down grass |
| Other signs | Grayish or pinkish fuzzy growth at snowmelt | Small holes about 1 inch across |
| Near | Snow piles, drifts, spots where leaves were left | Fences, beds, tall grass, shrubs, window wells |
You can have both at once. They show up at the same time, right as the snow melts.
UNDER THE SNOW • TWO DIFFERENT CONDITIONS
Gray Snow Mold vs. Pink Snow Mold
UMass Extension explains the two types:
| Gray snow mold | Pink snow mold | |
|---|---|---|
| Look | Gray, “lint-like” growth at snowmelt, with tiny brown specks | Pink to reddish-brown spots that fade to tan with a pink edge |
| Patch size | 1 to 3 feet across | Usually under 8 inches |
| When | Needs snow cover for about 45 to 60 days | Most often seen in early spring, and can form without snow cover |
| How bad | Usually kills only the leaves, and the grass regrows from the crowns | Can do more damage than gray |
NDSU Extension describes gray snow mold in North Dakota lawns as “matted down, straw-colored patches of grass,” sometimes with “cotton-like webbing.”
LOCAL FACTORS • SNOW • WEATHER • FALL CARE
Why Bismarck Lawns Get Snow Mold
Snow mold loves exactly what a Bismarck winter delivers.
- Long snow cover. Gray snow mold needs about 45 to 60 days under snow. Bismarck averages about 50.5 inches of snow a year, from about 8 inches in November to about 10 inches in December and 8 to 9 inches in January and March.
- Deep snow over unfrozen ground. UMass says both types favor “deep snow that prevents the soil from freezing.”
- Snow piles on the lawn. In Bismarck, you can’t push snow into the street or onto the boulevard. So it goes on your own lawn, often in the same spot every storm. Those piles melt last, and that’s where snow mold shows up worst. See the Bismarck snow rules for homeowners.
- Late nitrogen. UMass lists “high nitrogen levels” as a factor, and a University of Minnesota Extension educator says to avoid heavy nitrogen after mid-September.
- Tall grass and leaves left over winter. Long, floppy grass and wet leaves mat down under snow and hold moisture.
SPRING REPAIR • START AFTER THE GROUND DRIES
How to Fix Snow Mold in Spring
- Wait for the lawn to dry. A University of Minnesota Extension educator says to wait until “the soil is dry enough to support foot traffic.”
- Rake gently. Use a leaf rake to fluff up the matted grass. That dries it out and, as the same educator puts it, helps “suppress further fungal growth.”
- Spread out leftover snow piles so the ground under them dries and warms faster. UMass recommends snow removal and better drainage to speed spring drying.
- Give it time. Most patches just “take a little longer to green up in spring.” Gray snow mold usually kills only the leaves, and the grass grows back from the crowns.
- Reseed only what stays bare a few weeks after the rest of the lawn greens up.
- Don’t rush the fertilizer. NDSU’s first feeding of the year is around Memorial Day. See our lawn fertilization and weed control service.
Do You Need a Fungicide?
For a home lawn, almost never. The Minnesota Extension educator says “a preventative fungicide application in the fall is generally not recommended” and that fertilizing, mowing and raking “are usually all that is needed.” UMass also notes fungicides only work if they go down in late fall before the grass stops growing. Once you see snow mold in spring, a spray won’t undo it.
IDENTIFY VOLES • TRAILS • HOLES • BARK
What Vole Damage Looks Like
Voles are small brown rodents, about the size of a mouse, with small ears and a short tail. The University of Minnesota Extension says the most common ones in the region are the meadow vole and the prairie vole.
They stay active all winter under the snow, eating grass and making tunnels. When the snow melts, you see:
- Surface runways, a “series of criss-crossing trails” of dead grass
- Small holes about 1 inch across
- Larger dried-out patches where they fed heavily
- Chewed bark at the base of young trees and shrubs, with side-by-side grooves about 1/4 inch wide
The tree damage is the part to worry about. NDSU’s Extension forester says rabbits and voles kill more trees each winter than cold temperatures do. Our guide to protecting trees from rabbits and deer in winter covers guards that stop voles too.
RESTORE THE LAWN • THREE SIMPLE STEPS
How to Fix Vole Trails in Your Lawn
The good news: UMN says vole damage to lawns is “rarely permanent.”
- Rake out the dead grass in the trails once the lawn dries.
- Tamp down any loose soil in the runways.
- Reseed the bare spots. UMN says that as the surrounding grass grows, “it will cover up the trails.”
Most trails fill in on their own as the lawn grows. Bigger dead patches may need seed.
REMOVE COVER • PROTECT NEW TREES
How to Keep Voles Out
Voles want cover. Take it away and they move on.
- Keep mowing into fall. UMN lists trimming grass short as part of yard cleanup that discourages voles.
- Clear the edges. Cut tall grass and weeds along fences, beds and the foundation. UMN Extension also suggests cutting grass within 2 feet of young trees in late fall.
- Pull mulch back at least 6 inches from tree trunks, as Iowa State Extension recommends. Mulch against bark hides voles while they chew.
- Guard young trees with 1/4-inch hardware cloth, with the bottom 2 to 3 inches buried in the soil.
- Trap if needed. UMN suggests snap traps baited with peanut butter, set along runways. Keep traps and any bait stations away from kids and pets, and follow the label on any bait.
BEFORE WINTER • EIGHT JOBS TO REMEMBER
Fall Checklist to Prevent Both
Most of this goes on your fall to-do list anyway. Our fall yard checklist for Bismarck puts it all in order.
| Job | When | Stops |
|---|---|---|
| Last fertilizer of the year | Around Labor Day, before September 15 | Snow mold |
| Keep mowing until growth stops | Through October | Snow mold and voles |
| Final mow at about 2 inches | When the grass stops growing | Snow mold |
| Rake or mulch-mow leaves | October to early November | Snow mold |
| Cut tall grass along fences and beds | Late fall | Voles |
| Pull mulch back from trunks | Late fall | Voles |
| Guard young trees | October, before the ground freezes | Voles and rabbits |
| Spread out big snow piles and drifts | All winter | Snow mold |
NDSU says mowing until growth stops helps prevent snow mold. The UMN educator adds: avoid “excessive nitrogen fertilization after the middle of September,” rake leaves in fall, and spread out large drifts. If you’d rather hand this off, our fall and spring yard cleanup covers leaves, the final mow and spring raking.
TIMING • SPRING OR LATE AUGUST
When to Reseed Damaged Spots
- Spring: Rake, loosen the soil a little and seed once the ground warms. Most crabgrass preventers also stop grass seed, so don’t use one on spots you’re seeding. NDSU notes mesotrione is an exception.
- Late summer: Big areas do better with seed from late August to September 15, NDSU’s fall seeding window. Core aeration first helps the seed take. See aeration and overseeding in Bismarck.
If the spots don’t green up, or the grass looks yellow instead of dead, check our yellow lawn guide for other causes, like salt along the sidewalk.
Questions
Snow Mold and Vole Damage FAQ
Answers about matted winter patches, vole trails, recovery, fungicides, and fall prevention.
Need more winter answers?
Explore the snow and winter FAQ for more local questions.
What does snow mold look like?
Round, matted patches of straw-colored or gray grass that show up as the snow melts, sometimes with gray or pink fuzzy growth. Gray snow mold patches are usually 1 to 3 feet across. Pink snow mold patches are usually under 8 inches, often with a pink edge.
Will my lawn recover from snow mold?
Usually, yes. Gray snow mold normally kills only the leaves, and the grass regrows from the crowns. Rake the matted spots once the lawn is dry enough to walk on, then reseed any that stay bare. Pink snow mold can do more damage.
Should I use a fungicide for snow mold?
Usually not on a home lawn. A University of Minnesota Extension educator says a preventive fall fungicide is generally not recommended, and that fertilizing, mowing and raking are usually all that’s needed. A spray in spring won’t undo damage that’s already there.
What are the winding dead trails in my lawn after winter?
Vole trails. Voles feed on grass under the snow all winter and leave criss-crossing runways of dead grass, often with small holes about 1 inch across. Rake out the dead grass and reseed spots that stay bare.
Do voles kill grass permanently?
Rarely. The University of Minnesota Extension says vole damage to lawns is rarely permanent. Rake out the dead grass, and the surrounding grass usually grows in and covers the trails. Bigger dead patches may need reseeding.
How do I prevent snow mold this fall?
Make your last feeding around Labor Day, keep mowing until the grass stops growing, then make a final mow at about 2 inches. Rake up leaves before snow falls, and spread out big snow piles through the winter instead of letting them sit in one spot.
Bismarck Landscape
Need Help With Spring Lawn Repair?
If your lawn comes out of winter looking rough, we’ll rake out the snow mold, fix the vole trails and reseed what needs it. This fall, we can also set your lawn up so there’s less to fix in April.
You can also see our other contact options. For more lawn answers, visit our lawn care FAQ.