You've spent the past few months tending to your winter compost pile. Now spring's coming on and you are looking forward to using that black gold someplace in the garden. But how can you tell whether it's ready to use, or needs to cook for a few more weeks (or months) instead?
Generally speaking, compost is ready when most of the original materials have broken down enough to no longer be identifiable. That can take anywhere from a month to a year, depending on the materials, their original size, and how hot the pile stayed. Shredding your browns and greens before adding to the pile speeds things up considerably. Unshredded material, like eggshells or wood chips, can take more than a year to break down. Winter compost piles generally take longer than piles started in warmer seasons.
Signs that compost is ready to use:
The pile itself is smaller, about half the size it used to be.
The pile is no longer hot.
It looks like good soil: moist, brown and crumbly, not slimy or wet.
It smells earthy, with no odor of rot.
If you still aren't sure, put a couple of spoonfuls in a plastic bag, seal it, and check back in a few days. If it has that earthy smell, it's ready. If it smells off or unpleasant, it's still breaking down, and needs more time.
Don't forget to cure
Once a pile is no longer hot, it will still need a few weeks to cure. But the pile isn't just sitting, it's working. Curing allows the microbes and larger composters (like earthworms) that are active at lower temperatures time to do their work.
Using the finished product
To use, you can shovel the entire pile into your vegetable or flower beds and incorporate it into the soil or use it on top as a mulch. If you prefer a finer compost for seed starting or container plantings, screen out the uncomposted pieces and put those back in to cook with fresh materials. Having pieces of not-quite-finished compost is a good thing. The unfinished pieces will help inoculate the fresh material with beneficial microbes and start the decomposition process anew.
It's said that you can never have enough compost. In the unlikely event that you have more than you can use, and you want to start a new pile in the bin, you can shovel the finished compost into a plastic bag and store it elsewhere. That happy circumstance is a sign that you need to add more bins!
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