November is the month compost heaps go quiet. The heap that steamed, shrank and smelled faintly sweet all summer now sits still under a skin of frost, and the leaves pile up faster than you can process them. Plenty of gardeners look at that cold, silent heap and decide composting is a fair-weather job to restart in March. That is a mistake, and it costs a whole season of free soil improver.
Winter composting is absolutely worth doing, but it works differently from summer composting. The microbes that do the work slow down as temperatures fall, yet they do not stop entirely. A heap that is big enough, insulated well enough and fed the right mix keeps ticking over through the coldest weeks, and the work you do now sets up a rich, finished pile for spring. The trick is knowing what still breaks down in cold weather, what simply waits until March, and what should never go in at this time of year.
This guide covers the whole winter routine: how a cold heap behaves, how to keep its core warm, what to feed it and what to hold back, which system suits winter best, and a month-by-month plan from November to March.
What Happens Inside a Compost Heap in Winter
Composting is driven by microbes, and microbes are temperature-sensitive. In a hot summer heap, bacteria work fastest between about 40 and 60 degrees Celsius, and a well-built pile can hold that heat for weeks. As autumn cools, the pile drops through the mesophilic range, roughly 10 to 40 degrees, where fungi and a different set of bacteria take over. Below about 10 degrees, bacterial activity falls sharply, and below freezing most bacteria go dormant.
That sounds like the end of the story, but it is not. Three things keep a winter heap alive. First, the centre of a large heap is insulated by the material around it, so it can stay several degrees warmer than the air outside, sometimes warm enough for slow decomposition to continue. Second, fungi keep working at temperatures where bacteria have stopped, and fungi are the organisms that break down the tough stuff: leaves, twigs, straw and cardboard. Third, freeze-thaw cycles do physical work for you. Water inside plant cells expands as it freezes and ruptures the cell walls, so material that froze solid in January breaks down much faster once it thaws in March.
The honest picture is this: a winter heap will not finish compost in six weeks the way a summer heap can. What it will do is shrink steadily, stay active in its core, and arrive at spring half-digested and ready to finish fast. A heap abandoned in November arrives at spring as a cold, wet, matted lump that needs rebuilding from scratch.
How cold is too cold?
There is no single cut-off, because a heap is not one temperature: the outer 15 centimetres may freeze solid while the core sits at 10 degrees or more. As a rough guide, decomposition continues slowly down to about 4 degrees in the core and stalls below that. A compost thermometer pushed 45 centimetres into the centre tells you the truth in seconds. If the core reads above 10 degrees, your heap is working; near zero for weeks, and it needs more bulk, insulation or nitrogen-rich material.
1. Build the Heap Big Enough to Hold Its Heat
Size is the single biggest factor in winter composting, and it matters more than any additive or gadget. A small heap loses heat from every surface faster than microbes can generate it. A large heap has enough volume in its core to stay warm while its outer layers take the cold.
The widely used minimum for a hot heap is about one cubic metre, roughly 1 metre wide, 1 metre deep and 1 metre high. That volume gives the core enough insulation from its own outer layers to hold heat through a frost. Smaller than that, and the whole heap tracks the air temperature within a day or two.
If your heap is smaller than a cubic metre as November begins, you have three options: combine two small heaps into one before winter, turning and mixing as you go; top the heap up with autumn leaves and shredded cardboard until it reaches size, watering each layer; or accept a slower heap and use the trench-composting method later in this guide for kitchen scraps, so nothing is wasted while the main heap waits for spring.
Shape matters too: a heap wider than it is tall holds heat better than a tall, narrow cone, because it has less surface area relative to its volume. Aim for a low, broad mound with a slightly domed or covered top so rain runs off instead of pooling.
2. Insulate the Heap Like You Would a Greenhouse
Insulation is what turns a heap that freezes solid into a heap that keeps working. You are not trying to keep the whole heap hot, only to slow heat loss enough that the core stays above the point where microbes go dormant. The materials are free or nearly so, and most gardens already have them.
Start with the simplest insulation of all: a thick blanket of dry leaves or straw over the top, 20 to 30 centimetres deep. Leaves are plentiful in November, they trap air and shed rain. Pile them on loosely, and weigh the layer down with branches or wire mesh so the wind does not strip it. This one step can keep the core several degrees warmer.
Around the sides, stack straw bales against the bin, or bank up soil, old compost or bagged leaves against the walls. A double-walled bin, or a wooden bin lined with cardboard, holds heat far better than a single skin of slats with gaps. If your bin is open-slatted, staple old carpet, hessian or flattened cardboard to the inside faces before winter; the linings are biodegradable and will rot into the heap.
Cover the top with something waterproof but breathable: old carpet, a wooden lid, a weighed-down tarpaulin, or thick cardboard. The cover keeps heavy rain out, and rain is the enemy in winter: a sodden heap loses heat fast, goes airless and turns slimy. Leave a little airflow at the edges, though: a completely sealed heap goes anaerobic, smells bad and works slowly.
Where to put the heap for winter
If your heap sits in a frost pocket or deep shade, consider moving it before winter, or shielding it. A spot against a south-facing wall or fence, out of the prevailing wind, can be several degrees warmer than an exposed corner. Do not put it hard against the house wall, where damp and pests become a problem. If you cannot move the heap, a windbreak of straw bales on the windward side makes a real difference.
3. Feed It the Right Mix: More Greens, Smaller Pieces
The classic composting ratio is about 30 parts carbon to 1 part nitrogen, the famous 30 to 1. In winter that balance needs deliberate attention, because the materials change with the season: summer brings nitrogen-rich grass clippings, while winter brings a flood of carbon-rich fallen leaves and almost no grass. Left alone, the heap drifts carbon-heavy and decomposes very slowly.
The fix is to add more nitrogen-rich greens through winter and to chop everything smaller. Smaller pieces have more surface area for microbes and fungi to attack, and they hold heat better because they pack with fewer air gaps. A few minutes with secateurs or a spade, chopping kitchen scraps and shredding leaves, pays for itself many times over in faster breakdown.
Winter greens: what to add
Your kitchen is the main source of winter greens: vegetable peelings, fruit skins and cores, coffee grounds and filters, tea leaves and tea bags without staples, and eggshells crushed fine. Coffee grounds are especially useful: dense, quick to heat up, and available every day, they can supply a meaningful amount of nitrogen all winter.
Fresh manure is the most powerful winter activator if you can get it. A bucket of well-rotted horse or chicken manure, dug into the centre of the heap, can lift the core temperature within days. Use well-rotted manure rather than fresh if you plan to use the finished compost on food crops soon, and never use dog or cat waste, which can carry parasites.
Winter browns: what to balance with
Fallen leaves are the great winter brown, and November delivers them in bulk. Shred them before adding: whole leaves mat together into wet, airless layers, while shredded leaves mix freely and break down far faster. Run a mower over a pile of leaves, or stuff them into a bin and chop with a spade. Save a bag or two of shredded leaves beside the heap for use through winter, because by January the garden stops supplying them and the kitchen keeps producing greens.
Shredded cardboard, torn newspaper, egg boxes and the inner tubes of toilet rolls are all useful winter browns. Soak cardboard briefly before adding it, or it will sit dry and untouched for months. Straw, sawdust from untreated wood, and the contents of a pet rabbit or guinea pig hutch are also good browns. Avoid glossy paper, coloured inks and treated timber.
The winter ratio in practice
You do not need to weigh anything. The practical rule is simple: for every bucket of kitchen scraps you add, add roughly two to three buckets of shredded leaves or cardboard. Layer them rather than dumping one material in a lump, and water each layer lightly as you go. If the heap smells sharp and vinegary, it has too much green and needs browns. If nothing seems to be happening at all and the material looks dry and unchanged after a month, it probably needs more green and more water.
4. Keep the Moisture Right
Moisture is the winter balancing act: too dry and microbes go dormant; too wet and the heap goes airless, cold and smelly. The target is the same all year: a squeezed handful should feel like a wrung-out sponge, damp but not dripping.
Winter pushes heaps toward too wet. Rain falls on the open top, snow melts into it, and cold air does not evaporate moisture the way summer sun does. That is why the cover described earlier matters so much. Check the heap after heavy rain. If water pools on top, clear the cover and let the surface dry for a day. If the heap is sodden underneath, fork in dry shredded leaves or cardboard and leave the cover off for a day or two of dry weather.
Winter can also dry a heap out, oddly enough, if it sits under a roof overhang or a dense evergreen where rain never reaches it. A heap under cover still needs watering occasionally. In a dry spell, water the heap with a can, a little at a time, and check the core with a fork: the middle should be damp through, not dusty. Kitchen scraps add moisture on their own, so a heap that is fed regularly from the kitchen rarely dries out completely.
Snow itself is not a problem: a layer on the cover insulates the heap and melts slowly. The problem is the meltwater afterwards, so make sure the cover sheds water and the heap is not sitting in a puddle. Raise bins on bricks or pallets so water drains away, and never site a heap in a dip where water collects.
5. Turn Less Often, But Turn Smart
Turning a heap adds oxygen, mixes fresh material into the hot core, and speeds everything up. In summer, turning every week or two is good practice. In winter, the rules change: every turn lets a big puff of heat escape, and in freezing weather the heap may take days to recover the warmth it lost. Turn too often and you cool the heap more than you help it.
The winter rhythm is to turn every three to four weeks, and only on a mild day, ideally the mildest of the week. Fork the outside material into the centre and the centre out to the edges, so the cold outer layers get their turn in the warm core. Water lightly if the material is dry, then re-cover and re-insulate immediately.
Between turns, do not disturb the heap. Resist the temptation to poke at it every few days to see if it is working. The core needs stillness to hold its heat. A thermometer check once a week tells you all you need to know without opening the heap up.
If the heap has frozen solid, do not try to turn it: forking achieves nothing while the microbes are dormant, and risks breaking tools and tearing the bin. Leave it covered and wait for a thaw. When it comes, the material will be softer, the cell walls ruptured by the ice, and a single good turn will restart it quickly.
6. What to Keep Adding All Winter
The heap still needs feeding through winter, and the kitchen supplies a steady stream. Keep a small caddy or bucket by the back door so scraps make it to the heap instead of the bin. Add material little and often rather than in occasional huge dumps, which smother the heap and cool the core.
Good winter additions include:
- Vegetable peelings, fruit skins, cores and pips
- Coffee grounds and paper coffee filters
- Tea leaves and tea bags with the staple removed
- Eggshells, crushed fine so they break down faster
- Stale bread in small amounts, torn up and buried in the middle
- Shredded cardboard, newspaper and egg boxes
- Fallen leaves, shredded, saved in bags for use through winter
- Wood ash from a fireplace or wood burner, in thin sprinkles only
- Hair from brushes and pet grooming, in small amounts
- The contents of a rabbit or guinea pig hutch, bedding included
Wood ash deserves a note: it is alkaline and rich in potassium, and a thin sprinkle now and then is useful, but too much pushes the heap alkaline and stalls the fungi. A handful over a layer, no more than once a fortnight, is enough.
Bury kitchen scraps in the middle of the heap rather than leaving them on top. Scraps left on the surface freeze, attract rats and birds, and smell. A quick forkful of leaves over each addition keeps the heap tidy, warm and pest-free.
7. What to Leave Out Until Spring
Some materials break down so slowly in the cold that they are better kept out entirely. They sit unchanged for months, take up space, and can cause problems when they finally thaw.
Hold back these until spring:
- Thick woody prunings and branches, unless chipped or shredded fine
- Large quantities of sawdust or wood shavings, which are very carbon-heavy and slow
- Diseased plant material, including blighted potato haulms and mildewed leaves
- Weeds carrying ripe seeds, which may survive a cold heap and germinate in spring
- Roots of persistent weeds such as bindweed, couch grass and ground elder
- Cooked food, meat, fish and dairy, which attract rats in winter when other food is scarce
- Fats, oils and grease, which coat material and slow decomposition
- Glossy paper, coloured magazines and treated timber
- Citrus peel in large quantities, which is slow to break down and can deter worms
Diseased material deserves emphasis: a hot summer heap can kill many plant pathogens, but a winter heap cannot. Potato blight, clubroot-infected brassica roots and mildewed leaves will not be sanitised by a cold heap, and spreading the finished compost next spring would spread the disease with it. Bag diseased material for council green-waste collection, or burn it where allowed, and keep it out until the heap is hot again.
8. Pick the Right System for Winter
Not every composting system copes with winter equally well. The best system is the one that suits your space, your climate and how much material you produce. Here is how the main options compare in cold weather.
An open heap is the simplest system and the hardest to keep warm: it loses heat from every side and soaks up rain. It can work in a mild winter if big enough and well covered, but in a cold winter it usually stalls. Build it big, cover it well, and bank leaves or straw bales around the sides.
A wooden slatted bin holds heat better than an open heap, especially if the slats are close together and the bin is lined with cardboard. A bin also keeps the heap tidy and discourages rats. The best winter bins are the ones with a lid, because the lid keeps rain out and heat in. If your bin has no lid, a piece of old carpet or a wooden board does the job.
A plastic dalek-style bin is one of the better winter options. Its solid walls block wind, its dark colour absorbs winter sun, and its small footprint suits a small garden. The drawback is size: most dalek bins hold around 200 to 300 litres, well under the cubic metre that holds heat best. Fill one to the top before winter, insulate around it with straw bales or bagged leaves, and it will keep ticking over.
A tumbler is fast in summer and a mixed blessing in winter. Its elevated drum turns easily without spilling heat, but the drum is small, wind-exposed and thin-walled, so it cools fast. Fill it before the cold sets in, stop adding fresh material so the batch can finish, and wrap it in old carpet on the coldest nights.
A wormery is the indoor answer: red wiggler worms work happily in a garage, shed or utility room, turning kitchen scraps into rich worm compost all winter. Worms slow below about 10 degrees and die below freezing, so a wormery must live somewhere frost-free. For a household with no garden heap, it keeps composting going through the darkest months with almost no effort.
The comparison in short: for a large garden, a big insulated bin or heap is best. For a small garden, a dalek bin with straw-bale insulation is the practical choice. For no garden at all, a wormery indoors wins. And trench composting, covered next, suits anyone with a spare patch of bare soil.
9. Use the Freeze-Thaw Cycle to Your Advantage
Gardeners usually think of frost as the enemy of composting, but freezing does useful work. When water inside plant material freezes, it expands and bursts the cell walls. The material that comes out of a freeze is softer, wetter and far easier for microbes and fungi to attack. A pile of leaves that froze solid in January will rot noticeably faster in March than the same leaves kept frost-free all winter.
Use this deliberately: in late autumn, fill a spare bin or a stack of old compost bags with shredded leaves, kitchen scraps and a little manure, water lightly, and leave it out in the cold. Let it freeze and thaw all winter. By spring the cycles will have done much of the physical breakdown, and a single turn with fresh green material will finish the job fast.
The same principle applies to the main heap. Do not panic when the outer layers freeze. The core is still working, the frozen shell is insulating it, and the freezing is pre-digesting the material for spring. The heap is not failing. It is preparing.
10. Trench Composting: The No-Turn Winter Method
If your main heap is frozen solid, or if you have no heap at all, trench composting is the simplest winter method there is. It needs no bin, no turning and no insulation, and it feeds the soil exactly where next year's crops will grow.
Dig a trench about 30 centimetres deep in a spare bed, one spade wide. Fill it with kitchen scraps and shredded leaves, chop the material roughly as you go, and cover it with the soil you dug out. That is the whole method. The material rots underground, out of the frost, out of sight of rats and birds, and out of the rain. By spring, the trench will have sunk as the material broke down, and the soil above it will be dark, crumbly and full of worms.
Trench composting suits winter well because soil insulates far better than air: a trench 30 centimetres down stays several degrees warmer than the surface, and worms keep working through mild spells. It is ideal for a vegetable bed to be planted in spring: dig in November, fill through winter, and plant into the enriched soil in March or April.
There are two rules. First, keep meat, dairy and cooked food out of the trench, for the same pest reasons as the heap. Second, do not plant directly into a fresh trench. Give the material at least six to eight weeks to break down, and plant into the soil above it rather than into the scraps themselves, so young roots are not scorched by the decomposition process.
When to Expect Finished Compost
Winter changes the timetable. A summer heap built in June can finish in eight to twelve weeks; a heap built in November, fed through winter and turned a few times, will usually be ready in late spring, around May. That is not a failure, it is the normal winter pace, and the compost is just as good when it arrives.
You will know the heap is finished when the material is dark brown, crumbly and sweet-smelling, like forest soil. You should not be able to recognise the original ingredients, except for the odd eggshell fragment or woody twig. If you can still see leaves, peelings or cardboard, it needs more time. A handful should hold together when squeezed and break apart easily when poked.
Before using it, let it cure: move the finished material to a separate pile, cover it, and leave it for two to four weeks. Curing lets the microbial community settle, lets remaining salts leach out, and gives worms time to finish the job. Cured compost is gentler on seedlings and more stable in the soil.
Use the finished compost as a mulch around shrubs and perennials, dig it into vegetable beds before planting, or mix it with garden soil for containers. A 5-centimetre layer on the surface of a bed is a good general application. Do not use unfinished compost around seedlings: it can rob nitrogen from the soil as it continues to break down, and it can carry weed seeds that survived the cold heap.
7 Mistakes That Stall a Winter Heap
1. Letting the heap shrink below a cubic metre. A small heap tracks the air temperature and freezes solid. Combine small heaps before winter, or top up with leaves and cardboard until the heap is big enough to hold its heat.
2. Leaving the heap uncovered in the rain. A sodden heap goes airless and cold. Cover the top, keep the rain out, and let the heap breathe at the edges.
3. Adding whole leaves in thick layers. Whole leaves mat into wet, airless sheets that refuse to rot. Shred them first, and mix them with greens rather than dumping them in slabs.
4. Turning the heap on a freezing day. Every turn dumps the core heat you spent weeks building. Turn on mild days only, work fast, and re-cover straight away.
5. Stopping feeding the heap altogether. A heap with no fresh material has no fresh energy. Keep adding kitchen scraps little and often, with a brown layer over each addition.
6. Throwing diseased plants and seeded weeds into a cold heap. A winter heap never gets hot enough to kill pathogens or weed seeds. Keep diseased material and seeded weeds out until the heap is hot again.
7. Giving up in January. The heap looks dead, the core is cold, and nothing seems to be happening. It is not dead. The fungi are working, the freeze-thaw cycles are pre-digesting the material, and a heap that is fed and covered through January finishes far faster in spring than a heap that was abandoned.
Your Winter Composting Calendar: November to March
November: Build the heap up to at least a cubic metre. Insulate the top with a thick leaf blanket and line the sides with cardboard or straw bales. Fit a cover. Shred and bag spare leaves for winter use. Start feeding kitchen scraps with two parts brown to one part green.
December: Feed little and often. Check the core temperature weekly. Turn once on the mildest day of the month if the heap is not frozen. Keep the cover on. Start a trench in a spare vegetable bed for overflow scraps.
January: The quietest month. Do not turn a frozen heap. Keep feeding the kitchen scraps, burying each addition under leaves. Check the heap after storms and replace any insulation the wind has stripped. Plan where the finished compost will go in spring.
February: Watch for the first thaw. As soon as the core softens, give the heap a good turn and add a bucket of fresh manure or coffee grounds to restart it. Top up the insulation if it has rotted down. Start the wormery indoors if you have one.
March: The heap wakes up. Turn it properly, check the moisture, and add greens as the garden starts producing again. The bottom half should be close to finished: move it to a curing pile and start the new season's heap in the freed space.
Frequently Asked Questions
Can I start a new compost heap in November?
Yes, and November is a good month to start: leaves are plentiful, the soil is still workable, and a heap built now has all winter to break down before spring. Build it big, at least a cubic metre, layer greens and browns as you go, water each layer, and insulate the top. It will not finish before spring, but it will be well on its way.
Does composting really continue in freezing weather?
It continues slowly, and only in the core. The outer layers may freeze solid, but the centre of a large, insulated heap can stay above freezing, and fungi keep working where bacteria have stopped. Freeze-thaw cycles break down cell walls physically, so frozen material rots faster once it thaws. A heap that looks frozen solid is usually still working in the middle.
Should I keep adding kitchen scraps all winter?
Yes. Kitchen scraps are the main nitrogen supply in winter, when the garden stops producing grass clippings. Add them little and often, bury each addition under shredded leaves or cardboard, and balance each bucket of scraps with two or three buckets of brown material. Never leave scraps on the surface, where they freeze, smell and attract rats.
How do I stop my compost heap smelling in winter?
A bad smell usually means the heap is too wet, too green, or airless. Fork in dry shredded leaves or cardboard, leave the cover off for a day of dry weather, and stop adding greens until the smell clears. Make sure the heap can drain: raise the bin on bricks and do not site it in a dip. A healthy winter heap smells earthy, like forest soil, not sharp or sour.
Is it worth composting in winter if I only have a small garden?
Yes, and a small garden may benefit most, because every bucket of finished compost saves buying bagged soil improver in spring. A dalek bin filled before winter and wrapped in straw bales or bagged leaves keeps working in a small space. If even that is too much, a wormery in a frost-free garage turns kitchen scraps into rich compost all winter, and trench composting needs only a spade and a spare patch of soil.
When will my winter compost be ready to use?
Most winter heaps are ready in late spring, around May, if they were built big, insulated and fed through the cold months. Check for dark, crumbly, sweet-smelling material with no recognisable ingredients. Let it cure for two to four weeks before use, then spread it as a mulch or dig it into beds before planting. If the heap was small or neglected, it may need until early summer, which is still in time for summer planting.
The Bottom Line
Winter composting asks for less work than summer composting, not more. Build the heap big, insulate it with the leaves November gives you for free, feed it kitchen scraps little and often, keep the rain out, and turn it only on mild days. The heap will not steam and shrink the way it does in July, but it will keep working quietly in its core, and the freeze-thaw cycles will do much of the hard work for you. Come spring, while other gardeners are starting a heap from scratch, yours will be dark, crumbly and ready to feed the beds. That is a whole season of free soil improver, earned by a few minutes of attention on a cold afternoon. Start this weekend, before the first hard frost, and let winter do the rest.
