When I joined the University of California Master Gardeners of Napa County in 2016, I had planned to check out the MG committees and decide which one was best suited to my nascent talents. Jill Pahl had another idea: “Cindy, we could use you on the compost committee, right now.”

I was taken aback. Compost? Isn't that related to the rotting pile of organic matter in the southwest corner of my yard to which I add vegetable scraps but otherwise ignore? Shouldn't I be capering about in vineyards or rose gardens? I soon learned that while compost is not glamorous, it is fascinating. Composting creates a useful material out of waste, it avoids adding to landfills, and it reduces methane output. And I don't have to espalier it, either. I have been on the compost committee ever since.

The City of Napa has been ahead of the compost curve for years. Even if you don't have a home compost bin, you can put your leftover food and organic waste in your yard waste bin—including detritus like greasy pizza boxes and chicken carcasses, which you shouldn't compost at home—and the local garbage service will take it to its composting facility in south Napa, where it will join a pile as big as a city block and swiftly turn into the soil conditioner known as compost. But why not make your own compost?

In general, there are three types of backyard composting: hot (the UC Davis favorite), warm (the most frequently used), and cold (throw it in a corner of the yard and forget about it for a couple of years). With hot composting, you collect your materials---approximately equal amounts of dried leaves, shredded newsprint, chopped up twigs, chicken manure, green yard waste and kitchen scraps, which can be coffee grounds and eggshells and fruits and vegetables with no butter or oil—and put them in a compost bin and toss them with a garden fork a few times a week. Sometimes it is confusing what is green or brown. For example, coffee grounds look brown, but are considered green because they are nitrogen rich. Browns are carbon rich. According to the New York Times, if you sit it on your kitchen counter for a week and it starts to dry out, it's probably brown. If it starts to rot, it's probably green.

Cut your materials up first, using a knife, or a food processor, or for large amounts, a weedwhacker in a garbage can (wear a mask and protective goggles for this task). The smaller the pieces the faster the decomposition. The ideal size is 1 1/2” pieces, more or less. Add enough water so the mass is the consistency of a wrung-out sponge and you are on your way to producing a wonderful soil conditioner that will improve your soil's ability to absorb water and nutrients. This will give you healthier soil, stronger plants, and will conserve water. A hot compost pile, assiduously tended, can produce finished compost in four to six weeks. When the compost is ready, it will look dark and have an earthy, woodsy smell. You will be surprised at how much it has reduced in mass, too.

Warm compost is very similar, only you add the materials to the pile as you collect them. (You should bury new food scraps in the center of the pile to discourage vermin.) Keep the pile slightly damp and toss it once a week or so. It will take longer to produce compost--a few months--but warm composters aren't in a hurry.

Cold compost can take over a year. This is the method by which you keep adding to a pile, don't turn it, and after a few years say, “Hey, I wonder how the compost is doing?” You will find a deep, rich, dark decaying heap.

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You should sift your finished compost, to make it easier to incorporate into your soil. You can buy a round sifter (like gold miners use) online, and a five-gallon bucket anywhere, or you can make a sifter out of an old window frame and quarter-inch wire mesh like I did and screen it over your wheelbarrow. Wear garden gloves. In any case, any compost matter that doesn't fall through the mesh should be put back in the bin for further decomposition or used for mulch.

Note that while the garbage company can create compost out of meat scraps and other foods that contain fat or oil, home composters can't. Commercial compost gets very hot and can deal with bacon fat and chicken bones. Home compost generally doesn't get above 155 degrees, so you shouldn't add weed seeds or rose thorns to your compost, and leftovers with fat will only attract vermin. No pet waste, either! When people tell me “My compost pile smells awful!” I know that there is either an old cheese rind in there--or Fifi's feces.

There are all kinds of compost bins available, or you can make your own. Mine is dark plastic and thirty years old. Typical size is 27 cubic feet. I have seen bins made of wood, wire, and even a wide plastic tube standing on end with lots of holes in it. My grandmother kept hers in an old oil barrel and would roll it around to turn it. As the saying goes, “Compost happens.”

It is satisfying to make a useful product out of leftovers that would otherwise go to the landfill. If you are interested in learning how to make and manage your own compost pile, the first compost workshop of the year will be held on March 22, at Hagafen Winery. Sign-up information will be coming soon, in the space below.

QWEL Training: Napa County Landscape and irrigation pros are encouraged to become Qualified Water Efficient Landscapers. Earn this EPA WaterSense award-winning professional certification and save water and money for clients. The City of Napa is sponsoring free in-person QWEL training in English on four Wednesdays starting January 15. Space is limited. Register at quel.net/pub/class/491.

Planning a Cut Flower Garden: Library Talk, Thursday, February 6, 7-8 pm, via Zoom. Napa County Library. Register at the UC Master Gardeners of Napa County website, napamg,ucanr.edu.

Help Desk: The Master Gardener Help Desk is available to answer your garden questions on Mondays and Fridays from 10 am until 1 pm at the University of California Cooperative Extension Office, 1710 Soscol Avenue, Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number and a brief description of the problem.