DO IT YOURSELF: A GUIDE TO WORM COMPOSTING

PEOPLE OFTEN ASK ME about getting started with worm composting. After spending seven years as a keeper of worms, and a solid year or two engaged in a study of their habits and history, I still say that there is not a finer pet anywhere. I’ve had dogs that would not walk on a leash and birds that refused to sing, and at present I’ve got two cats who nap when they should be chasing mice and chase each other around the bedroom at night when I’m at risk of nodding off to sleep myself.

But a herd of worms will earn its keep, no doubt about it. They’ll take care of the garbage, fertilize the lawn, and bait your fishhook if you like to fish. They’ll provide the kids with science- fair projects and show-and-tell offerings for years to come. And they’ll do it all with a minimum of fuss and expense.

Plenty of books give advice on worm composting, and I won’t try to summarize everything they have to say here. Instead, I’ll tell you what I would want to know if I were setting up my first worm bin right now, and you’ll learn the rest as you go.

The first step is choosing a bin. It’s not difficult to locate instructions for making a worm bin out of scrap lumber or plastic storage tubs. After a trip to the hardware store and a stop at the bait stand, a homemade worm bin can be yours for twenty bucks, maybe forty.

But those homemade bins have a few downsides. Drainage is one concern. The worms won’t sit for long in soggy food, and you won’t like the smell if they do. It’s often hard to get a homemade bin to drain properly from the bottom and ventilate properly from the top, all while keeping the fruit flies out and the worms in. Harvesting castings is another problem: if the worms live in a single bed together with their food and castings, it can be ridiculously difficult to extract them. Some people say that if you shift the food to one side of the bin, the worms will follow, leaving the other side more or less vacant. But worms do tend to wander, especially within the confines of a small space, and it can take weeks for them to abandon one area of a small bin en­tirely, if they ever do.

There are many good commercially made worm composters out there—the Can-O-Worms, the Wriggly Wranch, and the Worm Factory, to name a few—designed to give worms the best living conditions possible and make it easy to harvest and use their castings. Some city and county recycling departments sell these worm bins at low cost; for instance, the county of San Mateo, where my uncle David lives, sells the Wriggly Wranch to county residents for a discounted price that makes it possi­ble for just about anyone to get into worms. In other counties, a recycling group or a university extension program might hold a composting or recycling fair and sell bins at a reduced cost for that day only. The Resources list in the appendix gives a few more suggestions for finding a suitable bin.

Once you’ve selected a bin, the next task is getting some worms. You can buy your worms from a bait stand as I did, but you’ll be better off ordering worms from a worm farm, which the leaflet that came with my bin instructed me to do. You’ll save a little money and you’ll have the assurance that you are getting the right worms. Besides, worm farmers are a friendly group, always willing to answer a few questions from their customers. If you live anywhere near a worm farm, you might even get a tour. (Be forewarned that some worm growers, fearing for their worms’ health, won’t ship live worms during hot summer months.)

It’s important to find a good location for the bin and introduce the worms to their new home as soon as possible. Some people keep their worm bins inside—under the kitchen sink, for instance—but one look at my husband’s face told me that the worms would live outside and that if I let even a few into the kitchen, I might be sleeping out there with them. My com­posters sit on the back porch, where they are sheltered from the rain and easily accessible to receive the day’s kitchen scraps. A garage is also a good location. Although my worms have never left their bins, one worm farmer I know includes a nightlight with every worm bin he sells, the idea being that even a small light will discourage worms from exploring your garage at night.

Most composters come with a coir brick that, when soaked in water, expands into a fibrous substance like peat moss. This goes in the bottom of the bin as a bedding material for the worms. If you don’t have coir, damp shredded newspaper or rice straw makes a good substitute. The worms will settle into their bedding, adjust to life in the worm bin, and get ready to eat.

Worm bins often come with instructions telling you not to feed the worms for the first few days, but if you’ve made it this far, you probably won’t be able to resist throwing a banana peel or a lettuce leaf their way to see what happens. That’s what I did, and I doubt it did any harm. This is the best way to start feeding worms anyway: a little at a time, giving them only as much as they can eat in a day or two. At first, a pound or two of food a week may be all that they can handle, but pretty soon they’ll be eating all your kitchen scraps, especially if you finely chop them so they’ll decay faster.

My worms have definite likes and dislikes, demonstrated by which foods are left to rot untouched in the bin, and which are covered in a mass of wrigglers within a few hours of being offered to them. They love banana skins, melon rinds, and lettuce leaves. They’ll eat coffee grounds and stale bread, but they won’t touch onions, oranges, or anything too acidic. They can’t eat fats in any form (including salad dressing), or meat, or dairy products. They do, however, like crushed eggshells because they provide a source of grit for their gizzards and help to moderate the pH level in the bin. No matter what you feed them, be sure to pile plenty of shredded newspaper on top to hold moisture in and keep fruit flies out. (Over the years, it has become a comforting part of my morning routine to deposit my coffee grounds and banana skins into the composter, then stand over them and tear up a section of the morning paper for them.)

Be prepared for a few critters to find their way into your bin no matter what you do. After all, the worms eat the micro­organisms—bacteria—that occur in the bin as food scraps decompose. A few creatures that are large enough to be seen may also start to show up, and they are harmless additions to the system. Pill bugs—roly-poly bugs—are always attracted to com­post piles and are considered a sign of good health in any composting system. Pot worms, or terrestrial enchytraeids, are often mistaken for baby earthworms. (Pot worms are white, but baby worms are reddish and faintly translucent.) The pot worms are closely related to earthworms and feed alongside them, causing no harm. And a small population of fruit flies may be inevitable, although they are also harmless.

Depending on the type of bin you have, your first harvest of worm castings could be weeks—or months—away. I rotate the trays of my Can-O-Worms about every three months, each time harvesting a few pounds of black, rich castings. By putting the tray to be harvested—the bottom tray, in my case—on top of the bin and leaving the lid off for an afternoon, the few worms that might remain in that lowest tray squirm away from the light and plunge down into one of the lower trays. I like to keep a stock of finished compost on hand, so my worm castings get mixed into a garbage can that also contains garden compost, manure, and other soil amendments from the nursery. I use this rich mixture—worm castings included—as a planting mix when I’m transplanting new plants, as an addition to potting soil, and as a layer of mulch in the vegetable garden. You can also dig worm castings directly into the soil or make a kind of compost tea by mixing the castings with water and using it to water your garden.

Most of all, though, if you keep worms, you shouldn’t be afraid to get to know them. Forget any advice you may hear about leaving your worm bin undisturbed. While I was writing this book, I found I couldn’t sit at my computer for more than an hour without going downstairs to check on the subjects of the book themselves. They are clean, quiet, well-behaved creatures, interesting to watch, and even beautiful in the way that any organism can be if you know just how to look at it. Put a worm in your hand and watch it expand each segment in turn, arch its back, flex its muscles. You will be won over. Lift up the top layer of food and newspaper in your bin and you will surely be awestruck at the spectacle of such industry taking place just outside your back door: thousands of worms churning through your apple cores and coffee grounds, your newspaper and dryer lint, taking it all in and turning it back into earth.