12 top composting faq’s
Q. Do I need to buy a bin to make compost?
Q. What can I put in the compost heap?
Q. What does not go into the compost heap? What materials can I not compost?
Q. Can I put weeds in my compost heap?
Q. What’s the easiest way to compost, without all the turning of the heap?
Q. How often do I turn the pile?
Q. How can I speed up the process? Is shredding a good idea?
Q. Can I use compost as mulch?
Q. What about “green manures” and composting them in place by turning them under?
Q. What about vermicomposting, or composting in worm bins?
Q. Where can I learn more about composting?
A. What method of composting you use should be determined by the volume of material created in the yard (and to a lesser degree, in the kitchen, where vegetable scraps, egg shells and coffee and tea grounds can be collected for the heap, too). I create far too much raw material for a typical homeowner-sized bin-type system, the commercially available kind made of metal or heavy plastic or mesh that are about as big as a washing machine.
I used to have one of those, a metal one that shut tight and thereby kept animals out, to hold my vegetable food wastes, alternating them with layers of garden debris and a little soil or finished compost to get things activated and reduce any chance of unpleasant odors. Now I just dig a hole in the main heap and bury food scraps or sprinkle soil on them to deter pests.
The latest rage is all about lobster-trap-wire bins, meaning really durable mesh (even under the ocean day in and out).
You can make an easy, inexpensive “pen” sort of bin with chickenwire and rot-proof stakes.
My main heap is about 40 feet long and 5 or 6 feet wide, a long, open pile that in composting jargon is called a windrow. In the peak of fall cleanup and leaf raking, it gets to be about 5 feet tall, too, but as the material begins to settle, and eventually to break down, it’s usually more like 3 to 4 feet high.
Garden author Lee Reich has a big garden, too, and he built 15 identical bins from notched, 4-foot lengths of “manufactured wood,” stacked log-cabin-style gradually, a tier at a time, as he adds material. He keeps piling stuff up in each bin to a height of about 5 feet, filling again a few times as the material settles. He moistens any dry ingredients slightly as needed when adding them. Lee used rot-resistant real lumber to build bins for many years, but lately had turned to the more long-lasting recycled decking “lumber.”
A. Whatever style of composting system you choose, from a simple, small pile to a long windrow to an enclosed store-bought bin, the key is to vary the kinds of materials that go into the mix. There is no precise recipe; there is just common sense at work.
Green plus brown equals black gold. Layer the two basic categories of ingredients: green ones (nitrogen-rich materials such as grass clippings and leafy green plants) and brown ones (carbon-rich materials like dry, brown leaves or twiggy bits and pieces). Too much of either one will impede decomposition.
I liken successful composting to the combustion that goes on when my car is running smoothly: to ignite, the car needs fuel, air, and a spark. So does the compost heap. The spark is the nitrogen-rich green stuff; the fuel is the brown stuff; the air is supplied by occasional turning of the pile, and water must be available from rain or the hose, so the pile is slightly moist but not sodden.
Too much green stuff (particularly wet things like grass clippings) will produce a smelly heap; spread them around, and toss in a thin layer of soil or old compost to help things get going. I don’t bother with store-bought compost starters; there are plenty of beneficial micro-organisms in good garden soil and some well-rotted leaves.
Too much brown stuff will just sit there (and that includes things that are “brown” chemically if not in color, like piles of orange rinds from weeks of juicing). Chopping up difficult brown elements will speed decomposition; so will aerating the pile, and adding more greens.
Manures from farm animals (not domestic pets) are great additions to the heap, if you can get them from a nearby farm or stable that does not use persistent herbicides or feed their animals any crops that have been treated with these chemicals. Otherwise, you can end up with “killer compost” that will retard plant growth; here’s that terrifying story.
Also remember that unless manures are well-composted in a fast-decomposing (or “hot”) pile, between 120 and 160 degrees F, they will be full of the seeds of what the animals were fed, so plan to let them rot thoroughly in a heap that’s really cooking along. A compost thermometer will help eliminate the guesswork here.
And don’t site the heap in the dark; a position in at least part-day sun is essential to good decomposition.
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A. It’s easier to list what doesn’t go in the heap than what does. Leave out:
- weeds with seeds on them (pull them before they go to flower and seed, when they can be composted, or “solarize” them to death first in plastic bags; see the next question);
- weeds that spread even without seeds (like bulbous onion grass), which can be solarized, too;
- diseased plants (though my expert friend Lee Reich does incorporate some, like this);
- fats and oils, such as dairy products and meats and fish; bones.
- animal manures from a tainted source (see the previous answer, or this story on “killer compost” or the U.S. Composting Council’s factsheets on the subject).
A. This list and how-to from Gardens Organic (England) is one of my favorites on what to compost and not to compost.
Scroll down on that great page (part of the most comprehensive composting site I know of) for the info on weeds/weed seeds, which includes this advice about bagging (to solarize/cook to death) the unwanted weeds, before adding them to the heap:
“Some perennial weeds will be killed in a hot heap; avoid really persistent horrors such as celandine, docks, bulbous buttercup, ground elder and bindweed. Don’t burn or dump these weeds–they are rich in plant foods. Mix with grass mowings in a plastic sack. Tie it up and leave for a few months until the weeds are no longer recognisable, then add to the compost heap. Or send them to your local council green waste recycling facility where the composting methods are hot enough to kill them off.”
The bagging idea is great–a sort of waste not, want not tactic for recycling them versus tossing them into the trash–and you can use a few bags over and again. The weeds I bag instead of adding right to the heap include any with strong runners (like goutweed, or former garden plants I now find too ambitious like plume poppy or ajuga) and any that have started to flower before I pulled them.
My longtime friend and fellow garden author Lee Reich puts weeds into his heap, though many expert sources say never to add diseased or insect-laden materials. Lee’s approach:
“I contend that if you look closely enough at anything, you’re going to find some ‘bad guy’ on it,” he says. “So my thing: I put everything into the compost.” Any and all organic material derived from a plant—“organic” meaning living or formerly living with an eye to adding both high-C high-N materials. He does turn each bin periodically, and again: His piles heat up to a temperature range (140 to 160 F) that helps kill off pathogens or pests.
A. Long before phrases like “lasagna garden” were making the rounds of the as-yet-uninvented internet, Ruth Stout (author of the classic “The No Work Garden Book”) was layering all her organic materials on top of her soil—sheet composting, as it might be traditionally called—to thwart weeds, reduce the need for fertilizers, conserve moisture and spare herself the work of composting in a conventional heap with all the toting and turning of materials.
Her approach to gardening starts with the foundational principle of applying mulch, mulch and more mulch, and then simply moving it back a tiny bit each year a bit to make room for a row of seeds rather than all that turning and tilling (and weeding).
She says the “aha” came one spring when the plow man hadn’t come yet to till, and she was eager to get planting. She saw that the asparagus (a long-lived perennial vegetable crop) was already up and growing, right through the layers of fallen leaves and such. “I walked over and said to the asparagus, ‘We don’t have to plow for you; why do we have to plow for the other vegetables?’” Stout recalls. “And the asparagus said, “You don’t.’”
Where do you get all that mulch? The garden creates it, or at least some of the raw material that becomes it: spent cornstalks and uprooted pea vines and the like, to which Stout added fall leaves and also bought-in straw or hay (“spoiled” hay was fine, and cheaper; don’t worry about a little decay).
So go ahead: compost in place. I think this is great for vegetable gardens more than ornamental beds, though, for aesthetic reasons.
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A. How often you turn your pile will affect the speed at which finished material is ready to be returned to the garden; if you’ve got time, you can escape turning and just let nature take its course (again, nobody’s perfect—and would you like to turn a 40-foot-long windrow every few weeks?). I turn twice a year, in spring and late summer or fall, and extract the lowest layer, where the finished stuff is hiding.
After 20 years of doing this by hand, I recently treated myself to a small tractor with a front-end loader, and the work will be easier from now on. Before using the compost in the garden, I toss it through a homemade sifter, into a wheelbarrow, to cull the stones and sticks and unfinished bits like tenacious corncobs or thick roots. I top-dress my flower beds with an inch or two of the sifted material each spring, along with some all-natural organic fertilizer, and use the rest to top up my raised vegetable-garden beds. Yummy.
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A. For years my friend Andrew has been telling me the secret, but I just wouldn’t listen. Like I do, Andrew creates a lot of debris from his giant garden. “Run it over,” he said, whenever I’d complain about the daunting size of my heap. “Just run it over with your mower to pre-shred the stuff.” Well, I finally did.
Facing the overstuffed, impossible-to-manage reality of my 40-by-6-by-8-foot heap, I raked the top 2-foot layer (the still-whole stuff, like last fall’s leaves) onto the ground beside the pile, removed any enormous or woody pieces, got out the tractor, and performed my first act of hit-and-run composting. Wow. What a difference a drive-by makes. Hit-and-run composting! Now I do this in fall when I collect debris, and also in spring cleanup. You could also invest in a shredder meant for this, of course, or an attachment to a leaf blower/vacuum if you use one.
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A. If you want to use compost as mulch later on, I recommend composting leaves separately, in their own pile, as they make a good mulch when partially rotted. Compost in its finest finished state is more soil-like than mulch-like texturally speaking, so not good mulch (but a great soil amendment).
Leaves can be shredded to speed up the process; this can be done if they are raked into small piles where the heap is to be made and run over with the mower, which works better when they are dry. Then moisten the pile and perhaps sprinkle in some soil or old compost. The leaves can also be left whole, in reusable bags or in a pile, all winter and shredded come spring. Leaf mold, as the rotted stuff is called, is both a great mulch and soil amendment.
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A. A month or so before killing frost, the vegetable-garden soil that fed me gets a meal, or at least the promise of one. I sow soil-sustaining cover crops (always from non-GMO, organic seed) as the various food crops are harvested, gradually turning my vegetable beds into mini-fields of winter cereal rye (above) and mammoth red clover for the colder months.
Come spring, several weeks before I plan to plant each area, I’ll cut the grain and legume down or mow them, depending on where they’re located, then turn under the remains—like composting in place, with the foliage and underlying root system decomposing to improve soil texture and fertility.
Cover crops can serve other purposes: Some specialized ones, like various Brassicas, can also provide not just biomass but other benefits like pest and disease control; the subject is much wider than this simple explanation but stated most simply:
- Grasses (like rye, sorghum-sudangrass crosses, and wheat) add organic matter to the soil very effectively (note that I don’t list buckwheat, another great cover crop, here; that rhubarb and sorrel relative is not technically a grass or grain, though we think of it as such because of how we use it food-wise);
- Legumes (clovers, cow and field peas, vetch) with their inherent Nitrogen-fixing capability, provide Nitrogen effectively;
- Brassicas and Mustards (rapeseed or canola; radish; mustard) have proven effective against various nematodes, fungi and insects.
Cover crops—there are varieties for each season and each climate—also serve as a living mulch, protecting the soil from erosion, and thwart other weeds, making the management of fallow garden areas (such as during crop rotations) easier than just standing back and watching undesirable plants take over.
Depending where you live, and what your purpose and timing is, here are some sources of high-quality seed:
- High Mowing Organic Seeds, in Vermont, has a dozen or more offerings.
- Peaceful Valley, in California, organizes them by type of plant (perennial, annual) and by purpose (e.g., erosion control, bug-friendly…).
- Bountiful Gardens in California calls them “compost crops;”
- Johnny’s Selected Seeds, in Maine offers many varieties, too.
- Cornell University has a longer list of sources, many commercial and geared to organic farming.
A. I haven’t written up this topic yet on A Way to Garden, but many years ago I read a book by Mary Appelhof called “Worms Eat My Garbage,” which is still the bible of vermicomposting. This is a great method for recycling food wastes even in an apartment setting, where there is no garden to compost in. One caveat: Worms sold for this purpose may be invasive and even damaging if let loose in the outdoor environment. The details.
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A. Favorite Resources: I am as proud of my compost heap as I am of any part of my garden. It is the archaeological record of my garden past; it is the stuff from which future gardens will arise. I read a lot about, from sources like these: Garden Organic, a 50-year-old British charity; Journey to Forever (don’t worry, not some into-the-bunker survivalist cult); and the vast Cornell Composting archive. The U.S. Composting Council is another mainstay. Dig in.
(Note: Shopping via the book links to Amazon in this article earn me a small commission that I use to buy other books for my giveaways here on the site.)
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