When the cold weather finally comes to an end and the foliage in your yard starts sprouting new green leaves, it can be frustrating if your grass doesn't follow suit. There are many reasons why grass may look dead after winter, and it often happens in a few patches (rather than affecting the entire lawn). This is commonly known as winter kill: It refers to any severe damage or death sustained by turfgrass lawns during the winter months.
The primary signs of winter kill are patches of lawn that remain brown or bare after the grass normally returns to healthy green growth in the spring. For the most part, turfgrasses that are well cared for will be resilient and strong, but winter weather can be unforgiving for even the healthiest lawns. The dead patches that have suffered winter kill can take months to fill in again on their own, and some causes may even require you to reseed or resod the lawn.
If your lawn has experienced dead grass after winter ends, find tips and treatment here for a variety of conditions.
Most grasses can survive just about any temperature range if they are blanketed with snow because snow acts as an insulator. However, uncovered grasses in very cold conditions will continue to transpire (lose moisture and oxygen) well after the ground is frozen solid. Frozen roots cannot replace the moisture sucked away by cold, dry winds, and the plants may suffer cell death and perhaps even death of the plant crowns.
Wait patiently as the growing season begins to see if the grasses return to health. If the damage is minor, individual grass plants may recover, or surrounding grass plants may fill in. With widespread damage, you will likely need to reseed or resod dead areas to restore the lawn to a unanimously healthy, green space.
When heavy snow falls over ground that is not yet cold, the moist conditions may foster a variety of fungal diseases collectively known as snow mold. When the snow melts in the spring, you may notice fuzzy or crusty patches (pink or gray in color) blanketing portions of your yard. Snow mold usually dies as sun and breezes dry out the lawn, but if the turf has been infected for a long time, the grass may die—but in most cases, grasses will gradually recover on their own.
If your lawn still has debris from the previous year, rake this up to improve air circulation to the grass. To prevent snow mold, make sure to de-thatch or aerate your lawn regularly to ventilate the grass and allow it to dry. Some experts advise against late-season fertilizing of the lawn because unabsorbed nutrients may foster mold when covered by snow while the ground is still warm.
The crowns of turfgrass can be killed if warm, moist weather is followed by a sudden freeze. This is a common reason that some grass looks dead after winter, and it happens most at the end of the cold season or during early spring—especially when unexpected frost occurs in warm climates planted with warm-season grasses. The plant crowns absorb water, so when they suddenly freeze, the fast expansion can kill them.
Widespread damage requires reseeding or resodding. There are not many ways to prevent the crowns from freezing. If you live in a borderline climate zone and your lawn has suffered crown freeze frequently, consider reseeding with a cool-season turfgrass blend.
A very identifiable type of winter kill is caused by voles—small rodents that leave narrow, meandering bands of dead grass on the lawn. The dead trails indicate the areas where voles have completely eaten away the grassroots.
Vole trails will usually fill in again as surrounding grasses send out new roots and shoots. With widespread damage, you may need to reseed. To prevent voles, make sure to remove dead grass and fallen leaves in the fall since this material offers the rodents shelter for their winter adventures. Voles can be trapped and baited in the same fashion as mice, though this is difficult to do with snow cover.
How to Prevent Winter Kill
When it comes to enjoying a fresh, green lawn each spring, one of the most important factors comes down to keeping your grass healthy before winter begins. Fertilize the yard in the early spring when grasses start actively growing, or after the last frost (depending on your region). It's also recommended to fertilize a second time in the fall, but be aware that fertilizing too late can cause snow mold if you live in a region that experiences heavy snow cover early in the winter. If your grass is prone to winter kill, it's also helpful to aerate your lawn during the growing season to prevent the soil from becoming compacted before cold weather sets in.
Winterkill of Turfgrasses. Pennsylvania State University Extension, 2018
Menken, J. How to Manage Vole Damage on Lawns, Trees and Shrubs. University of Minnesota Extension, 2019