What happens in my soil over the winter? (ASK Advice)

When winter rolls in and your lawn or garden goes quiet, it might look like everything has hit pause. Warm season grasses go dormant, and your yard might even be covered with a blanket of snow. But down beneath the surface, your soil is still very much alive—and, ultimately, winter always sets the stage for spring.

The soil ecosystem slows down

As temperatures drop, soil organisms like bacteria, fungi, earthworms, and insects naturally become less active. Some go dormant, some migrate deeper into the soil where it’s warmer, and others construct protective structures to survive freezing conditions. Microbial activity slows significantly, but it doesn’t completely shut down unless the soil is deeply frozen. So, organic matter added in fall (like leaves or compost) keeps decomposing at a reduced rate. This gradual breakdown contributes to nutrient availability for spring growth, when things warm up again and the soil ecosystem comes fully back to life.

What about plants? Cool-season grasses and many perennial plants continue limited root growth in late fall and even early winter, as long as soil temperatures remain above freezing. While top growth may stop, roots may still be storing carbohydrates and strengthening for spring. Once soils freeze solid, root activity largely pauses. But the plant isn’t dead—it’s simply dormant.

Ice breaks up soil structure

If you’ve had a snowy winter, or live downstream of snowy mountains, that snow acts as a slow-release water source as it melts in the spring. During the coldest months, snow cover insulates the soil, helping prevent extreme temperature swings and protecting soil organisms and plant roots.

In contrast, winters without snow are more prone to repeated freezing and thawing. Low temperatures draw soil water into pure ice crystal formations, called ice lenses. This ice breaks up physical soil structure, which is helpful if it’s loosening compacted soil. Otherwise, it can destroy stable aggregates in a soil with already healthy structure. Freeze-thaw cycles can even cause frost heaving. This phenomenon occurs when soil water freezes and expands upward, starting from the surface, pushing objects like stones, plant roots, and fence posts up with it.

In the spring, shallow soil thaws first while deeper layers are still frozen, increasing the risk for erosion and nutrient loss due to spring rains. This is one reason it’s helpful to have live roots in the ground as long as possible and avoid bare soil in your garden. Even after fall harvest, plant residues can help keep the soil in place over the winter until it’s time for spring clean up and garden prep!

Spring is on the way!

Winter is less about growth and more about rest, restructuring, and preparation. Soil organisms conserve energy, nutrient cycles slow, and physical structure resets. While your lawn or garden may look dormant above ground, by the time spring arrives, the soil has quietly undergone months of subtle but important changes below the surface. However slowly, winter has been at work to set up the next growing season.