By Carrie Knutson, Horticulture agent

NDSU Extension – Grand Forks County

Winter so far has been a rollercoaster of weather, with snowy and cold conditions in early December, followed by 40-degree Fahrenheit temperatures, the loss of snow cover, a return of snow, strong winds and then a repeat of the cycle. As a gardener, I’ve learned to appreciate snow cover during the winter, even when it means extra shoveling, because it plays an important role in protecting our plants.

How does snow protect plants during the winter? The answer lies below ground, in the roots and soil, and in the steps that we can take to help plants survive cold conditions.

Plants with shallow root systems are more susceptible to winter injury than those with deeper roots. Much of this damage occurs during cycles of thawing and freezing known as frost heaving. These cycles cause cracks to form in the soil, allowing cold air to penetrate and lower the soil's temperature. In some cases, roots are pushed closer to the soil surface, where they are exposed to extreme cold. Roots can be injured or killed when soil temperatures drop below 10 degrees.

Snow cover acts as an excellent insulator. It traps heat, helps the soil retain moisture and limits how deeply the frost penetrates the ground. Early snow cover is especially beneficial because it helps the soil hold warmth and moisture before the coldest temperatures arrive.

Even in winter, soil temperatures are typically warmer than the air above ground. For example, according to the Grand Forks NDAWN site, the soil temperature at the 12-inch depth today is 31 degrees, while the air temperature is just 4 degrees. This difference highlights the importance of insulation from the soil and snow in protecting plant roots.

Root injury is more likely during winters with little snow cover and extended cold, particularly when soils are dry. Moist soil retains heat more effectively than dry soil. So, when snow is absent, the cold can penetrate deeper into the soil profile, increasing the risk of damage.

Gardeners can take several steps to help plants survive the winter. One of the most important things is choosing plants that are suited to the USDA Plant Hardiness Zone for our area. The USDA Hardiness Zone Map was updated in 2023, and most of North Dakota falls within zones 3b to 4b. If you enjoy experimenting with plants outside their recommended zone, be prepared to give them extra protection, and keep in mind that one especially cold winter might be their last.

Mulching around plants is another effective strategy. Mulch helps insulate the soil, keeps temperatures more consistent and conserves soil moisture. Even something as simple as moving snow around your landscape to cover exposed plants during the winter can provide added protection.

I have mulch around several of my plants, and thanks to the blizzard a couple of weeks ago, I’ve accumulated enough snow in my backyard to help protect them this winter. Here’s hoping your gardens are well insulated, too. Happy gardening!

NDSU Agriculture Communication – Jan. 6, 2026

Source: Carrie Knutson, 701-780-8229, carrie.knutson@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu