How to Compost in Winter: 2 Big Mistakes and 6 Expert Tips

Every seasoned gardener knows, just because the seasons turn, that doesn’t mean the work stops. Whether you’re carefully tending a herb garden inside, cleaning out and reorganizing the long-neglected garden shed, or meticulously planning your garden layout for next spring, you’re always doing something…

And for many gardeners, that includes taking care of the compost!

Yes, you can compost in winter - and doing it well gives you a head start on spring. When temperatures drop, some gardeners abandon the compost heap until the thaw. Others keep it going all season, and they're onto something.

If you're an experienced all-season composter, tips like "build a bigger heap" or "get the green/brown ratio right" might feel like old news. But there are two big mistakes people make even after years of composting in winter, so we'll cover those first.

However, if you’re new to composting, don’t worry - we’ll walk through everything a beginner needs to know. After all, everyone is at a different stage in their gardening journey!

Why Compost in Winter?

There are several great reasons to compost in winter, including:

• Less waste: Kitchen scraps don't stop in November. Composting them year-round keeps food waste out of the bin. And even if your area does collect compost, why not use it for your own?!

• Better nitrogen retention: Organic matter held in a covered heap is less likely to leach away than scraps left on open ground.

• Improved soil structure: Finished compost adds organic matter that helps soil hold water and air. That’s great news for your future plants.

• A spring head start: Material added in winter is partly broken down by spring, so your first batch is ready sooner.

• Fewer trips to the green bin: One compost heap handles the whole season.

Winter vs. Summer Compost

How does winter compare to summer composting? Really, it just slows down. Composting is driven by bacteria, fungi and other organisms that break down organic matter. Like most living things, they work fastest when they're warm, moist and well fed.

As the air gets colder, that activity drops. A small or exposed heap may cool right down and even freeze solid during a long cold snap. A larger, well-insulated heap, on the other hand, can keep a warm core going well into winter, because the microbes generate their own heat as they work.

Either way, nothing is lost. A frozen heap simply pauses, then picks up again as temperatures rise. Freezing and thawing can even help: ice crystals break apart plant cell walls, so materials often decompose faster once spring arrives.

The goal of winter composting isn't to keep the heap roaring hot. It's to protect the heat and moisture you have, keep adding the right materials, and avoid the habits that set it back.

Winter Composting Mistakes

No matter where you are with your compost experience, there tend to be 2 big mistakes that people make in the winter - and they’re going to result in a less spectacular compost heap come spring. 

Here’s what to avoid:

Big mistake #1: Turning your compost too often

Turning is a crucial part of composting. It introduces oxygen, redistributes moisture and brings cooler outer material into the warmer centre.

In summer, you might turn a hot heap two or three times a week (sometimes even more). In the winter, this will work against you. Every time you open up the pile, warm air escapes from the core and cold air rushes in. In freezing conditions, the heap can take days or weeks to recover - if it recovers at all before spring.

If you're turning too often, you're doing your compost a disservice.

How often should you turn compost in winter?

Tips for turning in cold weather:

• Pick a mild day. Turn during a thaw or the warmest part of the day, never when the pile is frozen.

• Work quickly. Mix, re-cover and close the bin as fast as you can to limit heat loss.

• Check before you turn. Push a stick or compost thermometer into the centre. If it's still warm and doesn't smell sour, it's working - leave it alone.

• Turn for a reason. In winter, turn to fix a problem (a soggy or smelly heap) rather than out of routine.

Big mistake #2: Not protecting your compost from pests

We're not talking about insects here - they're part of a healthy heap. We're talking about mice, rats, squirrels, voles and other small animals.

In winter, a compost heap is one of the warmest, best-stocked spots in the garden. Rodents are drawn to the heat, the shelter and the easy food. Think of it like a fancy hotel! And once they move in, they can nest in the pile and spread to sheds and outbuildings. 

The good news is that a few simple habits make your heap far less inviting:

• Use a sturdy enclosure. Build your heap in a solid bin or raised bed rather than an open pile. A Sproutbox bed works well here - they're good for more than growing plants.
  
  
• Cover the top and base. Lay fine wire mesh under the heap and over the top, or use a fitted cover.
• Bury fresh scraps. Dig kitchen scraps into the centre and cover them with a layer of brown leaves, straw or soil to mask food odours.
  
  
• Skip the high-risk foods. Never add meat, fish, bones, oils, cheese or other dairy, or pet waste to a cold winter heap.
  
  
• Add an insulating top layer. A thick blanket of straw or dry leaves hides food, regulates moisture and holds in core heat.
  
  
• Keep it busy. Rodents prefer undisturbed spots. Checking the heap regularly - without over-turning it - makes it less appealing as a nest.
  
  
• Try natural deterrents. Some gardeners place cotton balls soaked in peppermint oil around the bed. Results vary, so treat this as an extra, not your main defence.

How to Compost in Winter: 6 Essential Tips

New to composting in winter, or haven't had much success in the past? These six fundamentals will keep your heap working through the cold months.

1. Build a bigger heap to hold the heat

A small heap loses heat quickly, while a larger one insulates its warm, active centre against freezing air. Aim for at least 1 m × 1 m × 1 m (about 3 ft × 3 ft × 3 ft) if you have the space.

If you're starting a new pile now, build it generously. Add material in batches rather than spreading a little everywhere — a thick layer heats up far better than a thin one.

2. Get the green-to-brown ratio right

Cold weather slows microbial activity, so the microbes you do have need a balanced diet. Mix:

• Browns (carbon-rich): dry leaves, shredded cardboard, straw, sawdust from untreated wood

• Greens (nitrogen-rich): vegetable scraps, fruit peels, coffee grounds, tea leaves, fresh plant trimmings

A useful starting point is two to three parts browns to one part greens by volume. Too many greens makes a slimy, smelly heap; too many browns makes one that barely moves.

3. Manage moisture

Moisture is one of the most overlooked parts of winter composting. Aim for damp throughout, like a wrung-out sponge - not dripping when squeezed.

• Shed excess rain and snow with a breathable cover, or site the heap under an evergreen for natural shelter.

• Too wet? Mix in dry leaves, straw or shredded cardboard and turn lightly to restore air pockets.

• Too dry? Add water sparingly during a mild spell.

• Check the centre, not just the surface. A dry outer layer can hide a sodden core, and the reverse is also true.

4. Insulate the heap

Insulation keeps the warm core working for longer. Wrap the sides of an open bin with straw bales, cardboard or old burlap sacks, and pile a thick layer of straw or leaves on top. A lidded bin or a fitted compost cover also helps protect the pile from cold winds.

5. Keep feeding the heap

Keep collecting kitchen scraps and suitable garden waste through winter. Chop larger pieces into small fragments so they break down faster.

If you can, keep a separate container of dry leaves or shredded cardboard next to the heap. That way you can balance every wet addition, even when the garden is under snow. Collecting autumn leaves in bags now is the easiest way to stock up.

6. Make it easy to reach

If the heap is at the bottom of a snowy garden, you'll stop using it. A kitchen caddy with a lid lets you collect scraps for a few days, and a cleared path to the heap makes winter trips quick. When snow is deep, you can store scraps in a sealed bin outdoors — they'll freeze — and add them to the heap during a thaw.

What to Add (and Avoid) in Winter

What are the best things to add to the heap when the temperatures drop, and what should be avoided?

The "moderation" items aren't harmful, but they break down slowly, change the pH or attract pests, so they work best in small amounts mixed with plenty of browns.

Troubleshooting Common Winter Compost Problems

Just as with summer composting, there are going to be things that pop up that can cause frustration. These are some of the common issues in the winter, and how you can solve them:

How Do You Know When Winter Compost is Ready?

Fast-forwarding to spring - how can you tell when that winter compost is ready for your garden bed?

Finished compost is dark, crumbly and smells earthy, like a forest floor. Check for these signs:

• The original materials are largely unrecognisable.

• The texture is loose and even, with no slimy patches.

• There's no noticeable warmth from active decomposition.

• It smells pleasant, not sour or like ammonia.

If you can still pick out scraps, find fibrous clumps or detect a sour smell, give it a few more weeks. Turn it if conditions allow.

If planting season arrives before the whole heap is finished, don't waste it:

• Use the mature portion as a light mulch around established plants or dug into beds.

• Return unfinished material to the heap or start a new pile with it.

• Keep half-decomposed compost away from seeds and seedlings. It can temporarily tie up nitrogen in the soil and may keep heating as it breaks down.

To separate finished compost from the rest, shake it through a garden sieve or a simple frame of wire mesh. The fine material goes into your beds; the lumps go back on the heap.

And don't be discouraged when things seem slow. Decomposition slows down a lot in cold weather, and a heap may become almost inactive during long freezes. That's normal - it doesn't mean your compost has failed.

The Payoff Comes in Spring

Composting in the winter rewards patience more than constant intervention. Build a generous heap, balance your greens and browns, keep moisture in check, protect it from pests - and resist the urge to turn it every week.

When spring rolls around, you'll have rich, homemade compost ready to fill your Sproutbox bed and give your plants the best possible start.

Happy gardening, friend!