Bob Mugaas, University of Minnesota Extension Educator
While the first few warm days of spring seriously tempt one to get out and do something in the yard and garden, patience may be the better virtue. One of the first tasks many people want to do is rake the lawn. Raking is a good idea as it helps to loosen matted down grass, thereby allowing sunlight and air to reach the soil surface. In turn, this helps warm the soil and stimulate grass into active growth. However, trying to do this too early when soils are still cold and muddy will unnecessarily uproot many healthy grass plants and contribute to increased soil compaction. Hence, the gardeners rule of thumb, stay off and avoid working in or on wet, muddy soils, applies equally well to lawns as it does to gardens. When the soil begins to dry out and is no longer soft and muddy under foot, that’s soon enough to attempt raking a lawn. Each lawn will be a little different in how quickly it starts to warm up and dry out. Monitoring your lawn’s condition every few days early in the spring will determine when its okay to be walking on it and raking can begin.
Photo 1: Snow mold on a Kentucky bluegrass lawn. Bob Mugaas
Once the snow leaves, many people discover areas of their lawn covered with small to medium size, circular, light tan patches of what appears to be dead grass. In some cases these circular patches will coalesce together forming large areas of dead appearing grass. This condition is caused by fungi that grow and thrive in cold, moist (but not frozen) conditions such as that found at the lawn / snow interface in late fall or late winter. We describe these symptoms as snow mold. In home lawns, most of this tan, dead looking grass is confined to the grass leaves and has not affected the actual growing points of the plant. This allows the grass plant to begin regrowth and, literally, outgrow the symptoms. In fact, a light raking to lift up the grass foliage again improving sunlight penetration and air circulation in the turfgrass canopy will speed recovery and stimulate growth. There is no need for any fungicide application at this time of year.
Photo 2: Meadow vole tunnels and ridges on a home lawn. Beth Jarvis
Another common over winter artifact visible in the lawn after the snow leaves are narrow, twisting ridges of loose grass blades that cover what appears to be a shallow trench. This damage is caused by a small, mouse-like animal known as a meadow vole. This is not damage typical of that caused by the eastern mole. By the time the snow leaves and damage is visible, the meadow voles have left the area for more protective cover. While damage from these animals can occur in many different lawn settings, they are most common where lawns abut other natural areas, unmaintained grassy fields, vacant, undeveloped lots and the like. Most of their injury is confined to damaging the grass foliage with little injury to the grass crowns which are responsible for regrowing new grass shoots and leaves. Simply raking off the loose grass blades and any clumps of uprooted grass plants will help stimulate new growth and recovery. If there are some areas where there was extensive vole activity and much of the existing grass uprooted, releveling of these spots, perhaps adding a little top soil, followed by overseeding will quickly repair those areas. While grass regrowth in the actual trenches may be a little slower than the surrounding undamaged grass, they will catch up even with little to no overseeding.
Photo 3: Deicing salt injury to Kentucky bluegrass. Bob Mugaas
Early spring is also the time of year when injury from deicing salts used on streets, driveways and sidewalks becomes apparent. Most often, this will take the form of a rather narrow band of dead grass adjacent to those hard surfaces. Sometimes it can also appear as larger dead areas next to the ends of sidewalks or driveways where snow from the street and/or driveway was piled. Turfgrass injury is usually the result of temporarily moderate to high concentrations of deicing salt in those areas. After a few spring rains or a couple of thorough soakings from a garden hose, these areas can usually be repaired by seeding or sodding without further salt related injury or death. There are grass seed mixtures that contain a more salt tolerant grass known as Puccinella distans along with other traditional lawn grasses known to be more salt tolerant. Two of the more common varieties of Pucinella distans are Fults and Salty. They will usually be listed on the container seed label and the mixtures are often sold as grass for boulevard areas or other areas that receive exposure to deicing salts. Repair seeding can usually be done as soon as the soil has dried out somewhat and is no longer muddy and soft under foot. Be sure to lightly loosen the soil surface such that seeds can easily be incorporated into it. Prepackaged “mulches” can also be used as additional protection for the newly seeded area. Follow package directions for proper use of the particular product.
For more information about these and other turfgrass problems, check out Extension’s Gardening Information website at http://www.extension.umn.edu/gardeninfo/. Click the “What’s wrong with my plant?” followed by clicking on the Turf icon.
Editor’s Note: The last two pictures are taken from the Gardening Information website from What’s wrong with my plant? under the Turf section (www.extension.umn.edu/gardeninfo/diagnostics/turf/index.html).