Visions of frozen coffee grounds and snow-covered orange peels? With the traditional northern-hemisphere gardening season at an end, many of us expect our compost to go dormant for the winter. As we wait for spring thaws to breathe new life into the earth, we pay little attention to those dormant layers of frozen plant matter.
Come planting time, we may find ourselves heading to the garden store to buy bags of commercial compost for our seedlings, as the microbes in our backyards have only begun to revive. Some opt for an indoor system, but bringing your compost into your kitchen is not the only option: if your outdoor compost is already cooking along nicely, you can keep it going with a few simple tricks.
Creating a self-contained ecosystem
By maintaining your compost throughout winter’s trials, you are supporting a year-round self-contained ecosystem. Your compost contains a wealth of living microbes, as well as hard-working worms who will die at temperatures below 40F. These worms generally protect themselves by burrowing deep underground in winter, but they don’t understand that your compost is above the ground, and will simply burrow as deep into the center as they can. Let’s help them continue their good work through the cold snaps!
Harvest any finished compost in the fall, so you will have plenty of room for the slower-decomposing additions of winter. Use your fall compost on houseplants, spread it on the lawn or perennial beds. Now you’re ready to start fresh! With a little preparation, you can have fresh finished compost ready for spring planting.
1. Location, location, location!
Just as bats prefer a warm, sheltered nook to roost, your compost microbes will thrive in similar conditions. Try to place your winter compost near or against an exterior wall or other wind buffer. Find out where your prevailing winter winds come from, and put the compost on the opposite side of the house, garage, or shed. Ideally, this will be on a south-facing wall where direct solar exposure will help warm it up on sunny days. Also imagine your winter trips to dump your kitchen scraps: you’ll thank yourself for planning a short route, maybe even within the reach of a porch light for those long January nights.
2. Bulk it up
It’s simple physics: any large mass takes longer to lose its heat than a smaller mass. The outer layers shield the inner core. Use those fall leaves blanketing the yard; they’re a fantastic resource for serious composters. Pull out all the spent annual plants from your garden and cut the wilted foliage from the perennials. This should give you a great head start after you’ve emptied all the finished compost for autumn mulching and fertilizing. Any bulky yard waste you add will have the added advantage of improving the texture and increasing internal air pockets, another essential insulating element. If you don’t have yard waste, you can add use shredded paper or cardboard, avoiding any glossy paper or colored inks.
3. Don’t let the frozen ground steal your heat
If you live in a climate with ice and snow, the ground beneath your feet becomes a vast storage system for cold. Anyone with any winter camping experience can testify that the layer between your body and the ground is the most crucial barrier for surviving an overnight in an icy climate: without a good sleeping pad, the frozen earth leeches away your body heat mercilessly. Your compost feels the same way.
If you have a tumbler, you’re already protecting your compost from the cold ground, but many commercial plastic composters sit directly on the ground. Raising yours up on a wooden pallet with straw or several layers of cardboard underneath is ideal; if this isn’t practical, make sure you add plenty of dead leaves, straw, or shredded paper in the bottom. If you like measurable data, you may want to buy a compost thermometer which will allow you to track exactly how the core of your compost is doing during various weather conditions. By collecting this information you can better plan for next winter.
4. Insulate for a cozy winter
Since compost makes its own heat, it may just need a little help to retain this warmth through the coldest months. If you have a basic heap or open pile, simply covering it up will go a long way. Build a little roof, or just use a tarp (a dark-colored tarp maximizes solar gain). Cover the top of your compost with a thick layer of straw or dead leaves (you’ll have to lift some of this insulating layer whenever you add new material). Some simple walls, made from fencing or pallets and lined with straw or cardboard, complete the containment.
If you want to get serious, try cinderblocks for the walls. An alternative strategy is to dig a hole for your compost directly into the earth — or even better, into the side of a hill — where the naturally warmer under-layers of the earth will keep it from freezing. Line the pit with straw or another carbon insulator.
Consider moving a tumbler or other portable contained system into a garage or outbuilding, where the walls will provide some measure of insulation. The Aerobin is actually designed with insulated double walls and is built for year-round operation. No turning is required with the Aerobin, making it an ideal low-maintenance, rodent-proof choice for many families who want to keep their compost active all year. An insulated tumbler is another tidy, low-odor choice for bringing inside. Both also work well out of doors. If you keep an uninsulated composter outside, you can pile straw bales or sacks of dead leaves around it.
What else can be used to insulate in winter? Snow! Though it may seem counter-intuitive, piling snowdrifts against all sides of your compost will actually help it maintain warmth inside — especially if you separate the snow from the compost with layers of cardboard or other neutral insulator. Snow maintains its internal temperature right around the freezing point: all the air between the crystals prevents any more extreme outside temperatures from passing through.
5. Balance your “greens” with your “browns”
“Greens” like kitchen scraps, weeds, and grass clippings provide nitrogen, while “browns” like dead leaves, wood chips, straw and paper products add carbon. Both are essential in relatively equal amounts — by weight. Get familiar with your local carbon sources, as we usually add plenty of nitrogen with our kitchen waste. Chop or shred any large chunks for best texture.
Remember your greens are typically heavier by volume (imagine a bucket of vegetable scraps versus the same bucket of dry leaves) so for every bucket of greens, sprinkle in 2-3 buckets of browns. Sprinkling is key, to avoid clumping, promote even mixing of the two elements, and add small insulating air pockets throughout. Adding the browns last as a top dressing also helps reduce odors and bugs.
Fall is a good time to reclaim any straw or other mulch that you’ve used over the summer on your planting beds. Leaving the decaying straw on your berry patch, for instance, may encourage fungal growth on the plants. Remember all these carbon-rich materials are harder to find (and more unpleasant to gather) during winter, so stockpile them now: fill several sacks with leaves, old mulch, or clean untreated sawdust and keep them in a sheltered spot near your compost for easy access.
Related: Use Autumn Leaves to Keep Your Composter Working Through the Winter
6. Stay moisture-aware: not too wet, not too dry
Depending on where you live, the moisture-regulation challenges will vary. For those in rainy climates like the northwest, soggy compost can become the norm in winter. Luckily, this is a solvable problem! The same roof or tarp which helps insulate your pile will also keep excess precipitation off. All your “browns” promote good drainage too. A moisture meter makes it easy to check without getting your hands dirty.
If your compost dries out, as in desert climates, your vital microbes will die. One advantage of winter composting is that drying out is rarely a problem — but if your area has extra low humidity, you may need to add moisture until the material is damp as a wrung-out sponge.
7. Use compost amendments
Should I buy a compost activator or compost inoculator? A compost activator is essentially a source of concentrated nitrogen, and is recommended only if you’re trying to compost large amounts of carbon-rich material such as dry leaves. Home composters rarely require such amendments, since we all have a great source of nitrogen-rich material in our kitchen buckets, assuming we eat at home. Fresh grass clippings are another abundant nitrogen resource if we have lawns to mow. If you’re looking for a particularly potent activator, try chicken manure or green comfrey leaves (not roots!), if you have either of these in your backyard!
A compost inoculator, on the other hand, contains helpful microbes to “jump start” the natural fermentation and decomposition process. These microbes are abundant in the natural world all around us, especially in the green and brown things we put in our piles and tumblers. If you’re concerned your compost is acting sluggish and may lack microbes, add a few handfuls of rich garden soil or finished compost from another source.
Good luck! Let us know how you’re solving your winter compost issues in the comments below. Thankfully, it’s a forgiving process, and even if your compost does freeze solid, warm weather will come to revive the eternal cycle. Our atmosphere thanks you for keeping your organic waste out of landfills, and your garden will reward you richly in due time.
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