Winter Composting
By Elaine Homstad, Fairfax Master Gardener
With the winter solstice having just passed, and with the anticipation of more cold weather over the next few months, it’s likely that gardeners here in Fairfax County and vicinity have put their gardens to bed by now. If you are an active composter, you added chopped up leaves, non-diseased plant material, and grass clippings from your final mow to your compost pile, bin, or tumbler. So when it comes to composting, you have nothing to do until next spring, right?
Well, even with the garden cleaned up and the leaves raked and composted, you still have a supply of kitchen scraps. And although the decomposition process will slow in the cold, there are still steps you should take to keep the pile active, particularly if your composting setup is open (pile or bin). Here are some basics of winter composting.
Maintain the green/brown balance
If you are adding kitchen scraps (vegetable matter only — no fats, meats, or dairy), you need to balance them out with brown matter such as dried leaves, straw, and plant debris. These can come from leaves you have bagged and saved or from houseplant trimmings (non-diseased only!). Absent that, you can buy bagged peat at your local garden center and use that instead.
On the other hand, if you have too many leaves to maintain the proper balance, just compost them separately with a combination of leaves and soil, piled together and loosely covered with plastic or a tarp. Passive composting will turn them into a nice organic addition for your garden soil.
Insulate the active pile
Keep the microorganism population alive and active by helping them to stay warm. If your pile is in a sunny spot, all the better. If you can enlarge the pile both on the sides and the top, insulating by using straw, newspapers, cardboard, or leaves, it is more likely that the center will stay active over the winter. In the spring, you should find plenty of ready-to-use compost at the bottom center of the pile.
If you have a screened bin, you could even build walls around it, as simple or as complex as you would like, using plywood, corrugated metal, bricks, or straw bales.
Watch the water
If your pile becomes excessively wet from rain or piled-up snow, your active microbes will “drown.” Although you can’t prevent uptake of soil moisture from the bottom of the pile, you can prevent extra moisture from falling on top of the pile by providing either a temporary roof over your exposed bin or a tarp covering your pile. The tarp will also help to keep a bit of heat in the pile, particularly if the sun shines on it.
Keep your kitchen scraps in your freezer
Rather than having to trek out to the pile in cold, wet, windy, icy or snowy weather, accumulate your kitchen scraps in a closed plastic bag in your freezer. That way you have not lost any of those valuable materials, and you can add them to your pile with a balance of brown matter when there are breaks in the weather.
Commercial composter
Rain is not usually a problem with one of these, since it is a sealed unit (albeit with ventilation openings). The problem you can run into in winter is an excess of green materials and a shortage of brown. This is where those reserved bags of leaves (or the addition of bagged peat) will help.
Another advantage to a sealed container is that it’s unlikely to attract wildlife that may, in search of anything edible, be enticed by and burrow into an open or more accessible bin or pile.
A compost tumbler is a very easy way to keep compost active through the winter because it is contained and elevated above the ground.
Consider indoor methods of composting
There are insulated sealed composter units you can use in your garage or basement, if you have the space and inclination. Or you could take up vermiculture, or worm composting.
Neither of these methods is going to produce enough compost for your outdoor garden, but many more people are taking up vermiculture, which can be a fairly inexpensive and interesting activity. You can read about vermiculture in our story, The Worm’s Turn by Doug Coffey.
So much of gardening is about the future — the beautiful blooms, the lush foliage, the bounty of fruits and vegetables — and keeping your compost active in the winter can give you a head start on the spring and summer growing seasons. And as any composter knows, the idea of continuing that circle of life, where the old replenishes the new in such a satisfying way, reminds us (with credit to Percy Bysshe Shelley) “… if winter comes, can spring be far behind?”
Resources
Backyard Composting, Virginia Cooperative Extension
Composting Your Organic Kitchen Wastes with Worms, Virginia Cooperative Extension
updated 2021