How to Compost in the Winter

Keep your compost cooking all winter long so you have fresh organic matter to lay down on your spring garden.

by Jessica Walliser

How to Compost in the Winter - Photo by Jessica Walliser (

Today is Christmas, so in most gardeners’ minds, it’s as good a day as any to talk about compost. Because winter has officially arrived, the only items most of us will have to add to the compost pile for the next few months are kitchen scraps, but that doesn’t mean your compost pile has the winter off. If you build your pile properly, it’ll be “cooking” all winter long—and you’ll have a fresh load of compost ready to spread come spring.

The benefits of composting your leaves, grass clippings, kitchen scraps and other yard waste are many. Compost is rich in nutrients and it readily improves the soil’s structure, allowing it to retain more water and drain better. A mere 5 percent increase in organic matter quadruples soil’s water-holding capacity.

One of the most important benefits of compost is the soil life that it supports. Be it bacteria, fungi, worms or beetles, these creatures help process nutrients and create healthier, more pest-resistant plants. Compost is a known disease suppressor, with university research pointing out that plants grown in soils regularly amended with compost have a marked reduction in disease, particularly those diseases caused by soil-borne pathogens. In a nutshell, compost promotes biologically active and diverse soil. Plus, it keeps a lot of yard waste out of the landfills.

The first step in getting your pile to properly “cook” all winter long is to build it with the right ratio of ingredients. There are two basic classes of ingredients constituting a well-balanced compost blend: the carbon suppliers and the nitrogen suppliers.

  • Carbon suppliers are materials added to the compost pile in a non-living state. They are usually brown in color and have low moisture content. Carbon suppliers are slow to decompose, so they take longer to fully break down. All those autumn leaves fit into this category, as does shredded cardboard, newspaper, straw, hay and sawdust.
  • Nitrogen suppliers are those ingredients used in a fresh state. Nitrogen suppliers are often green in color (except in the case of manures) and have high moisture content. Because they contain many sugars and starches, they are quick to decompose. Nitrogen suppliers include untreated grass clippings, plant trimmings, manures, spent garden plants and kitchen scraps.

The proportion of these two ingredients (known as the C:N ratio) is a decidedly important factor in determining how well the pile breaks down and whether or not it continues to “cook” throughout the winter. If you have too much of one ingredient and not enough of another, the pile doesn’t “cook” as well. Basically, the pile should contain about 30 times more carbon than nitrogen (a C:N ratio of 30:1). This ideal ratio is accomplished by building a pile that contains two to three times more carbon materials than nitrogen materials (by volume). So for every 5-gallon bucket of fresh green grass clippings, three 5-gallon buckets of straw or leaves will also have to be added. I save many of my autumn leaves in a side pile through the winter and gradually add them to the grass clippings throughout the summer.

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Another thing you should add is some of last year’s finished compost as you create a new pile. This increases the population of the organisms that break down your compost and introduces them to the pile faster.All these microbes use oxygen and exhale carbon dioxide while decomposing, which means it’s an aerobic process. To maintain aerobic conditions, oxygen must be provided by turning or otherwise aerating the pile on a regular basis, even in the winter. Whenever my pile gets turned—even in February—it’s steaming hot in the center, “cooking” away and getting ready for spring.

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