This spring began with the very early snowmelt in mid-March that left in its wake one of the highest incidences of snow mold on many residential and commercial lawns in recent memory. Much of that could be attributed to the very wet snow that fell around Christmas time on unfrozen or barely frozen lawn surfaces. The high moisture content of the snow combined with the mostly unfrozen lawn conditions provided nearly ideal conditions for the snow mold fungi to grow and thrive. In addition, that snow cover was maintained throughout the winter months providing a very long period of total snow cover and good conditions for snow mold growth. However, as is often the case, even with as much snowmold as was evident this spring, most lawns will have recovered on their own and returned to healthy growth and good green color by early May. The severity of snowmold on some lawns did result in the need for some reseeding to fill in thin areas resulting from that injury. Photos 1 and 2 show a commercial site affected with snowmold earlier this spring that has now grown out of those symptoms without the need for reseeding or other repair. A light application of fertilizer and some watering as needed this spring will help further restore and invigorate those areas.
Meadow vole damage and recoveryThat continuous snow cover over winter also created a good habitat for meadow voles to invade our lawns resulting in slight to extensive surface tunneling in lawns, especially those close to unmaintained grassy areas such as next to vacant lots, prairie edges or other nearby grassy areas where voles retreat to after the snow melts. See Photo 3 for typical injury associated with meadow voles in lawns. For the most part, these critters tunnel along the surface eating a variety of vegetative material including the grass. One may observe tunnels traveling over and through the lawn surface. It is often common to see loose grass 'clippings' mounded up over the tunnels creating a slightly raised appearance to the seemingly random tunnel patterns. While the grass foliage is eaten by the voles, the grass plant crowns (growing points) often escape being eaten and are responsible for the regeneration of new leaves and stems that ultimately fill in the tunneled areas. Since the plant is having to start from scratch in its spring regrowth, the tunneled areas frequently lag behind the rest of the lawn area in spring recovery but do ultimately catch up to the rest of lawn in terms of height and density. See Photo 4 of new grass shoots coming in a surface tunnel caused by voles. Again, a light application of fertilizer and water as needed will help restore the growth and vigor of these areas. In nearly all cases, recovery occurs without the need for reseeding or replacing the damaged areas.
Early season mowing
Crabgrass arrives early too!
Once crabgrass has emerged from the ground and is visible, it is too late to apply preemergence herbicides for crabgrass control. These products act on the newly germinating crabgrass seedlings prior to their emergence from the ground. In this case, one will need to use products containing the active ingredients quinclorac or fenoxaprop-p-ethyl. Both of these are available through commercial lawn care firms. Quinclorac can also be found in some homeowner lawn weed control formulations. Check the product label for its list of active ingredients. For very small infestations, it may be practical to manually remove them. In either case, treating the seedlings while they are still small and tender is much more effective than when plants are larger and more mature.
Just because you may have already observed some crabgrass germination in those heat sink areas, it doesn't necessarily mean you shouldn't apply a preemergent crabgrass control product to the rest of the lawn area if it's needed. However, it should be applied very soon, like within the first week or so of May, depending on your specific site conditions. Soil temperatures in the main lawn areas will lag behind those in heat sink areas, but they do catch up fairly quickly as temperatures continue to warm, especially overnight temperatures. Even though crabgrass germinates earlier in those warmer soils, it doesn't germinate all at once. Hence, an application of preemergence herbicide in those heat sink areas can help prevent later germinating seeds from getting started but won't kill those already sprouted.
Easy-does-it for spring fertilizing
Usually about the time the lawn is greening up and in need of its first mowing is a good time to consider applying a spring application of lawn fertilizer. For many of us, that time may have already passed. However, that doesn't mean it's too late to fertilize the lawn. In fact, sometime within the first three to four mowings of the year is still a good time to fertilize. Regardless of the situation, it's wise to not be aggressively fertilizing your lawn in the spring, especially with large amounts of nitrogen. That's best left for the late summer period.
In the spring, there is a natural, normal flush of growth by our grass plants. It begins with active root growth followed by rapid shoot growth. As shoot growth begins to accelerate, root growth tends to slow down. If too much nitrogen fertilizer is applied, shoot growth will be even more rapid resulting in a more frequent need for mowing but is also unhealthier for the grass plant. Excessive growth stimulated by too much nitrogen creates a more succulent plant that in turn requires greater amounts of moisture to sustain its growth. That increased succulence is more vulnerable to injury from summertime stresses and can be more prone to certain disease and insect infestation. The bottom line is, use moderate to low amounts of N in the spring to maintain balanced, but healthy, turfgrass growth. For more information on lawn fertilizing, see the publication Fertilizing Lawns (http://www.extension.umn.edu/distribution/horticulture/DG3338.html).
Water if needed to support early season growth
While we often don't think of watering our lawns much before sometime in May, this year, due to the drier than normal conditions and earlier than normal vigorous grass growth, watering may be needed to sustain healthy, early season turfgrass growth. Early spring is the time of year when grass plants are actively growing new and deeper roots. That allows the plant to mine water and nutrient reserves from a larger soil volume, which, in turn, sustains the continued healthy growth of new shoots and roots. At this time of year watering deeply but infrequently is a good practice. Thus, an inch of water per week (or longer interval depending on weather conditions) including any rainfall that occurs will help keep soils moist and promote healthy root growth. If you have heavier, more clay-like soils where it takes a long time for water to infiltrate into the soil, it's usually best to apply a couple of lighter applications allowing time in between for the water to soak into the soil. Likewise, on lighter sandy soils that drain more rapidly, infiltration is not so much a problem as is the likelihood of water moving too quickly down through the soil and beyond the grass plant's roots and therefore not benefiting the grass plant. Hence, a split application of water will also be more beneficial for the grass on sandy soils.
While spring has indeed arrived ahead of most years, the tasks of lawn care remain much the same except that they need to be carried out earlier than many of us are used to. Paying attention to prevailing weather conditions and observing what's happening in your lawn are very valuable aids when it comes to understanding what's going on and what to do next.