How to Compost in Winter: 7 Expert Tips

Compost is one of the greatest investments you can make in your garden! It turns raw waste into valuable humus-rich soil perfect for trees, shrubs, and crops. No matter where you live, you can compost, meaning anyone can turn rotting apple cores and old leftovers into soil amendments. 

Winter is challenging for decomposition, as the process requires warm temperatures to thrive. If the pile freezes or grows excessively soggy, it’ll slow down the organisms that help decompose waste. The goal is to keep your pile actively decomposing so it’s warm, alive, and steaming with activity from October through March.

These seven tips ensure your winter compost pile stays active so you can continue adding food scraps, fall leaves, and plant debris. No matter your decomposition goals, this is a good way to start achieving them. So, let’s dive into a pile to see what goes on underneath the surface. 

Make A Bigger Pile

The first step towards protecting your compost is to make it bigger. Combine multiple small piles into one larger pile, or add new waste materials to an existing pile. The larger size protects the inner parts, as they have insulation from the outer layers.

This large heap will grow warmer than small ones during wintertime, staying active on the inner parts. Ensure it stays big by adding new debris as the organisms eat the old waste. The biological activity releases heat, which warms the pile as it wafts away as steam.

The ideal decomposition heap size is three feet wide and tall. Increase the size during winter to five or six feet wide and tall so the pile traps heat instead of releasing it.

Correct the Ratio

Oftentimes, decomposition issues result from improper ratios. Balance is key, as compost requires 30 parts carbon to one part nitrogen by weight. Different waste materials have more carbon or nitrogen, depending on their makeup. 

Composters break up waste into two different groups: greens and browns. Greens are fleshy plant materials rich in nitrogen, while browns are dead ones rich in carbon. Use this chart to identify common greens and browns you can use:

Because most browns are lofty and less compact than brown materials, you can use a simple trick when layering the ingredients. For every shovel full of greens, you’ll add two to three scoops of browns to compensate. This ensures an even balance that results in the desired 30:1 carbon-to-nitrogen ratio by weight. 

Turn Less Often

Frequent turning is a crucial maintenance task for hot compost piles. It ensures air flows regularly, exchanging carbon dioxide for oxygen. Turn by taking a pitchfork and stabbing it into the bottom layers, lifting and turning them over. You shuffle all the decaying organisms so they can breathe before finding new things to eat. 

It’s still important to turn piles during winter months. However, you’ll want to do it less frequently. Turning allows pent-up heat to escape in the form of steam. The steam will waft away on a cold winter breeze instead of insulating your heap.

For hot piles, turn once or twice a week. Turning is less important for cold piles, as they work at lower temperatures and for more time than hot piles. Ensure you turn cold mounds once a month throughout the frosty months. 

Regulate Moisture

Regular moisture is the key to composting success, but too much winter moisture drowns the decomposition organisms! You’ll want to regulate your pile so it stays around 50-60% moist. This means when you pick up a piece of the decomposing matter and squeeze, it’ll feel like a wrung-out sponge. If excess moisture falls from the clump, your pile may be too wet.

Wet piles are frequent during the winter, especially in regions like the Pacific Northwest, where it rains frequently in fall, winter, and spring. Exposed piles are subject to rainfall, which turns a perfectly moist heap into a soggy one. 

Especially if you live in a region where moisture is constant in winter, place your compost under an evergreen tree, a patio cover, or other structure that prevents rain from getting into it. This way, you can control how much water it receives to ensure it feels like a wrung-out sponge. 

Protect the Pile

Rain protection is beneficial for winter composting piles, although so is protection of other sorts. Hungry rodents and small mammals may frequent the decaying waste in search of a meal, and birds may pick through the top layers.

Like rain, snow threatens compost with freezing temperatures and excess moisture. Hot compost piles usually burn the snow with steam before it collects, although cold piles may gather thick layers of snow. Place the compost underneath a shelter for the winter, that way you can control its inputs and prevent unnecessary stress from rain or snow.

To keep rodents out, first, ensure you’re not adding smelly materials like rotting meat or dairy products. These attract rodents by the dozens. Consider adding a thick layer of leaves, straw, or other carbon-rich waste materials on the outside of the pile to protect the inner parts from animals. The thicker, the better, as more non-smelly waste on the outside presents a larger blockade for pesky rodents. 

Remove Invasive Species

As freezing temperatures arrive in fall and winter, decomposition slows throughout the natural world. The slow process allows more weed seeds, roots, and shoots to persist in composting piles. This makes for a challenging spring, as any area you put the compost may erupt with weed seedlings.

It’s easier to add weeds and seeds during spring and summer, as hot compost piles may kill them and prevent them from returning. You may want to reconsider this during the winter and choose to leave invasive plants and their seeds out of your piles. Bury them deeper than a foot underground, or dispose of them using your local green waste program.

One note here: if you plan to compost invasives in the warmer seasons, ensure they are plants that will actually break down in a compost pile before you do.

I still throw weeds in my compost piles during the winter. If weed seedlings sprout in the spring garden, I remove them and let them decompose on top of the soil. This allows them to morph into valuable humus for other plants while preventing their spread. It takes some work and weekly upkeep, but the free garden benefits are worth it! 

Know It’ll Be Slow

My last piece of advice is this: practice patience! Cold temperatures, no matter how much work you do, mean a slower composting process. Piles you make in the fall may not be ready until early spring or later, depending on whether you’re hot or cold composting. 

Extra resources are abundant during autumn, as leaves fall to the ground and plants put on a final growth spurt before winter. Use these extra materials in compost and you won’t regret it—you’ll turn useless waste into an invaluable resource for your garden.