Q. I'm starting two compost piles and am wondering how often I should turn them. I decided to clean up our side yard—it hadn't been touched in about eight years—and collected a lot of leaves that I figured should make perfect compost for my veggie garden. So I shredded them all up and put some in a compost tumbler I inherited from my grandfather, and the rest in a simple 'plastic fence' style composter (the kind some extension offices give away or sell for cheap). I thought it would be best to just leave the piles alone and only turn them once or twice a month, but my father says I should be turning them every three days. How often should I turn my compost? And should I turn the tumbler more often than the "pile"? Love your show!
- ---Jonathan in Northridge, CA
The answer to your question is what I like to call "the Dirty Little Secret of Composting." If you mix up the correct ingredients—that's mostly well-shredded dry brown materials like your absolutely ideal super-perfect fall leaves and a much smaller amount of nitrogen-rich 'green' materials—and moisten those ingredients as you go, I see no need to turn a pile that's in contact with the ground more than once or twice. Total.
What I typically do is make a large number of such piles in the Fall; some in composters made of recycled black plastic, some in wooden bins, many in wire cages (including my out-of-season tomato cages); and let them cook for a while. How long is 'a while'? Depends on the weather, my compost needs and that darn 'real life' stuff that's always getting in the way. (Plus, I no longer seek out hard labor the way I used to back when I was young, foolish, virile and foolish.)
Now if my compost needs are high and my supply low, I'll mix up a fast, 'hot' batch. I'll combine a double size amount of well-shredded leaves and a HOT nitrogen source (like a couple of five gallon buckets of spent coffee grounds) in a big, five-foot tall wire bin that's about four feet across with a 'chimney' in the center (a tube of the same wire fencing about ten inches in diameter). I'll even water this pile if it doesn't get rain.
I'll watch that baby cook—you can see heat waves above the chimney—for about a week or two. Then I'll lift off the outside cage, remove the chimney and pitchfork the contents over into the same cage (now positioned a few feet over), refilling it. Typically, the bottom half of this 'new' pile will be finished compost a week or so after that. At that point, I'll remove the cage for the final time, mix any unfinished stuff from the top into another bin or three, load the finished material from the bottom into a wheelbarrow and use it.
Now, this is great compost; 'hot compost'. Compost that's made quickly, with just shredded fall leaves and a hot source of nitrogen like coffee grounds or horse or poultry manure, has the most nutrients and disease-suppression powers. But let's get real. I dutifully do the work of collecting and shredding enough leaves every year to fill about 40 good sized piles or bins, and I feel that this earns me the right to slack off on making it all 'hot'. Now I still make those other piles correctly—by shredding and mixing the ingredients well and in the right proportions—but I use mostly 'cold' kitchen waste as their green component and then just let the piles sit until the Spring.
By then, the material on the bottom is finished compost despite my laziness and the winter cold. I use the best of the material from the bottom right away, then mix all the un-composted and half-finished stuff into one or two big new piles. This material is primed from its previous cooking time, and the weather is warming, so these piles are generally fully composted and ready to use a couple of weeks later—which is, honestly, about as soon as I want to be pushing that wheelbarrow again.
Now, there's nothing wrong with turning an above-ground (i.e., non-tumbler) pile once a week or so; it's good exercise and makes better quality compost. And if you're using one of those recycled black plastic composting units, you don't even have to work as hard. Just use a shovel to extract some of the material from that convenient 'coal chute' they all have at the bottom and shovel it back onto the top. Water it afterwards if the cover excludes rain (some do; some allow it in) and/or you're in a dry clime.
Tumblers, spinners and other non-ground-contact composters are a different story, however. Because of their design (and the fact that they don't allow earthworm access), they should get a spin or a turn of the crank every day or so. The payback is that—again, if the mix of materials inside is correct—they typically provide hot, high-quality finished compost in a very short period of time. Don't forget to water these types regularly, as the contents tend to dry out much faster than piles that touch the earth.
But whatever you do, be sure and get ready to make some of your own super-soil this Autumn. Because those precious leaves only fall once a year and that time is coming soon...