Composting in the Autumn: 6 Simple Steps

Composting projects started in the autumn are an important part of any organic garden. In the early stages, compost gives you something to do with expired plants, grass clippings, kitchen waste and other organic materials. By next summer, the compost you start now will be ready to dole out to pots and planting beds as a bioactive soil amendment.

Autumn-to-spring composting follows nature’s weather cycles, so it’s a slow process that may last six months or more. Cold winter temperatures suppress biological activity in compost, but repeated freezing and thawing destroys tough plant tissues, which better prepares them to rot. If you’re a new composter, check out Ben’s perfect compost recipe for a great introduction. Then get composting!

1. Gather Spent Plants

Aged vegetable plants that are sputtering along but no longer truly productive are best pulled up and piled together in convenient little heaps around the garden. The leaves, stems and roots may harbour insects or diseases, but pulling up the plants interrupts the party because most pests need a live host to survive. You can toss expired plants into your main compost pile, or let them shrink in little heaps before adding them to an enclosed composter. With old plants out of the way, you may have time to plant a soil-building winter cover crop in the newly vacated space.

Should you have plants that are infested with aphids or other mobile insects, quickly stuff the entire plants into a large plastic bag to keep them from dispersing. Close the bag tightly and place it in the sun for several days before composting the dead plants and bugs.

2. Start a New Compost Heap

Build a big new pile, or start a new container composting project in a bin or tumbler. If you are refilling a tumbler or composting bin, dump out and store the old compost, but don’t clean the container. Microbes stuck to the walls will inoculate your new composting project, so dirty is good!

When choosing a site for a new outdoor heap, keep in mind that the soil under the pile will benefit from the microbes, insects and nutrients from the pile. An autumn composting project is a great way to break in new gardening space.

3. Collect Leaves

As an act of insect conservation, it is best to let leaves rest where they fall, because many insects from tiny gnats to big butterflies overwinter among fallen leaves. But some leaves land in inconvenient places, and these can be gathered in bags or simply piled up and composted alone or with other composting materials for future use. Leaves removed from outdoor stairs, sidewalks and driveways add up quickly when collected in a pile.

Never be in a rush to compost leaves, because the first stage of leaf decomposition is weathering. Until tannins and other compounds are washed from leaves by repeated rains, they won’t begin to rot. Leaf type is a factor, too. Thin or small leaves weather quickly, while thicker leaves take much longer to start breaking down.

4. Boost Your Compost

Include manures from chickens, rabbits, or other animals you deem safe and desirable. When added to compost in autumn, manure provides needed nitrogen for the mix, and the months-long composting process ensures that unwanted bacteria in manure will be long gone. Do be careful when sourcing horse manure, which can contain herbicide residues from feed hay that damages tomatoes, beans, and other garden crops.

5. Go Big!

Keep adding material to your autumn compost heap every chance you get, because large piles work much better than small ones. The best compost heaps exceed one cubic yard or metre in size, which can be a challenge to create because of constant shrinkage. Do the best you can, and don’t worry if the heap gets smaller rather than heating up. In spring, when the mass is reduced and the weather is warm again, you have the option of re-composting your material in a hot composting project to kill weed seeds and worrisome microorganisms.

6. Rest Your Compost

Compost straight from the heap or composter is great, but cured compost, which has been set aside to rest in a semi-dry state, is even better. I like to fill several large empty flowerpots with any finished compost left from the previous year, which I store outdoors protected from rain. In spring, when the main compost pile is just waking up, I use the stored compost to prepare beds for early plantings.