Although your lawn is dormant during the winter months, there are still things that can be done to improve the appearance of your lawn once it greens up again.
Core aeration is a great item to check off on one of those winter days when the ground is not frozen. Aeration loosens up the soil underneath your grass that has become compacted over time. Soil compaction can cause your soil to dry out, which leads to decreased nutrient uptake and possible drainage issues.
Sod or Overseeding can be done on days above freezing to fill bare patches in your lawn as long as you water well afterward.
Fertilizing is still helpful during the winter; you can feed your lawn with lime if a soil test shows it is needed or apply a slow-release fertilizer.
Raking is always a good way to keep your lawn healthy because leaves stuck on your lawn all winter can lead to pests, fungal growth, and bare patches.
Weeding can be done in late winter when it starts to warm up and the early weeds begin popping up. They are easy to spot and remove by hand or you can use a pre-emergent.