As with everything in nature, composting has its seasons and autumn is one of them. It can be tempting to forget the compost pile once the main gardening periods of spring and summer are out of the way, but to do so is to miss out on the opportune time for gathering one of its most bulky of ingredients: carbon.
The nitrogen-carbon ratio in a compost pile should be around 1:30 i.e. one part nitrogen to 30 parts carbon. Nitrogen comes largely in the form of green materials: weeds, kitchen scraps, vege trimmings and lawn clippings. These ingredients are abundant in spring (when we’re cleaning up the garden ready for planting and sowing) and summer (when we’re busy harvesting and consuming produce, and mowing lawns). In summer we also have easy access to animal manure (which provides both carbon and nitrogen) because we’re not having to stomp through wet grass and muddy fields to collect it. But spring and summer are also the times when we have least access to the bulk of the carbon component of compost piles.
Carbon consists of ‘brown’ materials and, not surprisingly, given their colour, we have greatest access to them during the months of autumn. Brown materials take the form of dead leaves, dry grasses such as straw and pea straw, spent vegetable material such as bean and cucurbit vines, and corn stalks. As autumn is also the time for cutting back perennials that have finished flowering, and lifting dead annuals, there is also plenty of carbon available from the ornamental garden. With less to do in the garden itself, autumn is a time for venturing further afield in search of ‘brown material’ in the form of fallen pine needles and leaves piled into drifts by autumn winds. As animals are brought closer to home, often being housed indoors, at least for part of the time, by late autumn and winter, gardeners on small blocks and larger farms can also look forward to a regular supply of animal manure mixed in with bedding material such as straw or sawdust. Pure sawdust is also available as we cut wood for winter fires.
The difficulty with autumn composting, however, is that we seldom have access to enough green nitrogen-rich materials to layer in with our ready supply of ‘browns’. But the beauty of carbon material is that, because it is usually dry, it can be stored for later use. To do this, I pile animal manure and bedding material into one pile (which will grow in size over the colder months) and store dead vegetable matter in wool fadges. Once they are full, I cover them with a water-proof tarpaulin.
Whenever I have enough green material for a layer in the compost pile, I haul out some of the dry brown material and pile it on top.
As the days begin to cool and the composting worms retreat to the warmth of the interior of the pile, give some thought to how you can best insulate your compost. If it is usually exposed to the elements, covering it with old carpet can help hold in warmth. If you live in a rainy part of the country, black plastic will hold in heat while also keeping the pile moist rather than wet.
Rather than being a time to forget the compost pile, autumn days are perfect for gathering and stockpiling the myriad different carbon-rich materials that make up the ‘perfect pile’. And come spring, no one will be more pleased than you that you got out and harvested the ‘brown stuff’.