What happened to my lawn? It was lush, thick and dark green at the end of the growing season and now it's covered in brown patches—some with white and yellowish spots, other areas look like the grass has packed its bags and left. Don't worry, odds are that it's suffering from one of these common forms of winter lawn damage: snow mold, salt damage or vole damage, and can be repaired.
Table of Contents
- Snow Mold
- Common Causes of Snow Mold
- Snow Mold Treatment
- Snow Mold Prevention
- Reduce the height of your cut as the growing season ends
- Clear leaves in the fall
- Use a fertilizer that’s low in nitrogen
- Treat Compacted Soil
- Avoid piling snow too high
- Salt Damage
- Treating and Preventing Salt Damage
- Vole Damage
- Treating and Preventing Vole Damage
- Snow Mold
- Salt Damage
- Vole Damage
Snow mold, also referred to as snow rot, is a fungal lawn disease that is active underneath snow cover during the winter months. It typically appears as a matted area of grass with web-like fuzzy strings, or mycelia, in-between grass blades. These circles of matted grass and web-like fungus can be gray or pinkish in color and can appear as smaller patches throughout the lawn or as one large intertwined collection of patches.
There are two types of snow mold; gray snow mold (Typhula Blight) and pink snow mold (Microdochium Patch). While these two types of snow mold look similar, their effect on the grass is different. Gray snow mold typically only affects the grass blade and in most cases will recover fully as the grass grows through the spring. Think of this as being like a scratch in a finger nail. As the nail grows it pushes the affected area out and replaces it with healthy new growth. Pink snow mold, on the other hand, is more aggressive and kills the crowns and roots of the grass of the affected area.
Common Causes of Snow Mold
For people in areas where snow cover lasts until early spring, snow mold is a common issue. The main cause of snow mold is a layer of material that blocks the soil surface from light and locks in moisture. This layer can be created from several things: either your grass was too long at the end of the growing season and it folded over on itself creating a matted area, the leaves from fall weren’t properly cleared or the layer of thatch in your lawn was too thick. When snow piles up in the winter, it takes longer to melt than the rest of the snow. These snow piles create an environment where moisture is prominent and light can’t penetrate to the soil to help dry the area. When this is coupled with a layer of dead leaves or a thick layer of thatch, it creates an ideal situation for snow mold to form. With this in mind, snow is not required for snow mold to form, it’s just one of the most common scenarios that creates ideal growing conditions for the fungus. A lawn with too thick of a layer of dead leaves or thatch located in a cool, rainy and overcast environment can also become affected.
How to Treat Snow Mold Damage
Most cases of snow mold are cosmetic in nature, and typically only effect the grass blade. These cases typically fix themselves as the grass grows and new growth replaces the affected growth. Lightly raking will help loosen up the matted area and allow for new growth. However, be careful, raking too aggressively can kill the grass. Some cases of pink snow mold may require you to reseed the area as Pink Snow Mold kills the crown and root of the plant.
There are chemical treatments available for extreme cases, but most of these fungicides aren’t recommended for residential use and should be used as a last resort, only to be used if prevention tactics have failed.
An organic method to remove snow mold, other blights and diseases is solarizing. This is when you place a clear piece of plastic over the snow mold patch. This allows the sunlight to heat the soil enough to kill the disease, essentially creating a greenhouse effect. The Gardeners Guide to Common-Sense Pest Control recommends doing this to every area you plan on replanting each season. Doing this will help give you a clean slate for the soil you’re planting your grass in.
Reduce the height of your cut as the growing season ends
Slowly lower the height of your mowers cutting deck as the growing season ends. You want to make sure that by the end of the fall your lawn is no longer than 1-1/2” to 3” at the longest. The shorter your lawn is at the end of fall—the less likely it is to fall over on itself causing matting. Make sure that you lower the height of your cut slowly to not cause trauma to the lawn, remember the 1/3 rule.
Clear leaves in the fall
Making sure that you diligently remove leaf build up in the fall helps remove the conditions where Snow Mold thrives. Make sure you remove or mulch your leaves in the fall and keep your layer of thatch less than 2” thick. Snow mold growth is most prominent under covers that hold moisture, a pile of leaves or a thick layer of thatch will provide an ideal growing condition for this mold, especially under a pile of snow.
Use a fertilizer that’s low in nitrogen
Make sure you end the season with the proper fertilizer. If you use a fertilizer that is rich in nitrogen to end the season, it will provide the lawn with nutrients that can promote blade growth into early winter. This can cause the grass to grow after your last cut leaving you with longer grass than you should have for the winter.
Treat compacted soil
As snow begins to melt in the spring the residual water needs to drain somewhere. Making sure that your soil is properly aerated will help ensure that it can properly drain. If water collects on the surface it will keep any matted grass or thatch moist which can lead to the formation of Snow Mold.
Avoid piling snow too high
When snow is piled excessively high, it takes longer to melt in the spring than areas where it’s naturally accumulated. These residual patches of snow block sun from reaching the soil and trap moisture under them. Try to avoid piling snow as much as you can.
In situations where piling snow isn’t avoidable it’s very important to remember that all leaves have been cleared and that the layer of thatch in your lawn doesn’t exceed 2”.
The other common type of winter damage is salt damage. In areas where road salt is used as a de-icing material the spray created from the melted road salt can run off into your lawn or can be splashed or sprayed onto your lawn or landscaping from the street. Salt spray from trucks can travel upwards of 150 feet. Even if you don’t use rock salt as a de-icing material on your drive or walkways, your lawn can suffer from salt damage if you live on a street that is treated with rock salt.
Typically salt damage is the result of the salty brine that is created when melting snow and ice gets splashed onto surrounding plant leaves or runs off into the soil of the surrounding area. Occasionally, you can visually see the salt deposit on the soil as a white or yellowish brown crust on the soil surface. When there are elevated levels of salt found in the soil, it can create drought like conditions even though there is plenty of moisture in the soil. It can also create a symptom called leaf burn, or leaf scorch, as the levels of chloride increase to toxic levels in the plants leaves.
Salt Damage Treatment
Recovering from the negative effects of salt as a de-icing material can be tricky, as once the damage has been done, there is little you can do to reverse it. Depending on the extent of the damage, treatment can vary from a complete removal and replacement of the turf to less intensive soil top-dressing and over-seeding. Typical treatment involves applying Gypsum (in pelletized form) and thorough watering of affected areas. This will help flush the soil of excess salts.
Is it dead or dormant? As the seasons start to change it may be hard to tell if a patch of grass is dead or still dormant from the winter. An easy way to check this is to tug on a tuft of grass from an affected area. If there is no resistance and the roots come up, then the area is most likely dead. If you feel some resistance, then odds are that the roots are still strong and the area is still just dormant.
The best treatment for salt damage is to take proactive measures to avoid it. If you want to prevent salt damage at home, make sure you choose the correct de-icing material. Choosing a calcium chloride-based de-icing material will help prevent causing damage. These materials are less harmful to plant-life. Shoveling or clearing snow before you apply your de-icing material will also help reduce the amount that seeps into your lawn. If you live in an area that is regularly treated with rock salt in the winter to remove ice and notice annual damage to your landscaping you may need to consider planting more salt tolerant species of plants.
Damage from vole “runways” or paths is a very unwelcome sight when snow starts melting in the spring. Many people are blissfully unaware of the damage that is being created under the snow, until the snow melts in the spring. Though it appears dramatic, especially when coupled with one or both other forms of winter lawn damage we discussed, it’s mostly cosmetic in nature. In most cases, the lawn will regrow in the damaged areas as the weather warms up.
Vole damage is primarily caused by feeding. Voles typically chew the plant down to the crown (or growing point) at ground level. Additional damage is caused by the traffic created by the voles during feeding and the accumulation of excrement along the “runways” or paths. This damage commonly occurs during the winter as snow cover provides good protection from predators and allow voles to travel from the nest to the runways to feed and back, stealthily creating the damage you see in the spring.
When it comes to repairing winter weather damage, prevention is the key. Follow these tips to avoid winter damage before it starts and save yourself the extra work in the spring.
- Maintain a well kempt lawn
Slowly lower your average height of cut as the season ends. Make sure you mow until the lawn finishes growing for the season and make sure the last cut of the season is shorter than your average.
Make sure you’ve diligently cleaned any leaves and make sure your layer of thatch isn’t too thick.
- Choose the right De-Icing material
Choose a calcium chloride-based de-icing material for use around your home and make sure you apply it after clearing snow.
- Relocate possible vole nesting sites
Find and relocate any wood piles, compost piles, brush piles and other sources of cover for voles to nest in.