Do you want to build the soil life in your garden? An easy first step is raising worms. Vermicomposting is the process of using worms and microorganisms to turn kitchen waste into a black, earthy, nutrient-rich humus. A garden’s soil food web—protozoa, nematodes, bacteria, fungi—needs a humus layer in order to access nutrients in the soil, and practicing vermicomposting is one way to build humus in your soil quickly and sustain it over time. The fertilizer produced from a vermicomposting system is called worm castings. Worm castings contain high levels of phosphorus and potassium, and are rich in humic acids, microorganisms, and help improve the structure of any soil to which it is added.
First, we need to talk worms. Most folks in Tucson are using red wigglers (Eisenia fetida) for vermicomposting. These worms thrive in rotting vegetation, compost, and manure. They are epigean, a term used to describe organisms who are active above the soil surface; in this case, by crawling. They are rarely found in the subsoil and seek out conditions that other worms couldn’t survive in. They do very well in containers. Like all other worms, red wigglers are hermaphroditic, but two worms are still necessary for reproduction. The clitellum, the band on a worm, is a thick saddle-like ring that secretes a thick fluid that forms a cocoon for their eggs. To reproduce, two worms must join their clitella and exchange sperm, and then both worms secrete their cocoons
Red wiggler worms thrive at temperatures of 59 to 77 degrees, but can survive temperatures between 50 to 86 degrees. It is easiest to establish a worm bin inside, since it will require fewer inputs to keep them alive in our hot summers and cold winters. Indoor worm bins can be made from food-grade (No. 2 or 5) storage totes or five-gallon buckets. I suggest placing your worm bin in a dry and cool place, like in the laundry room, under kitchen sink cabinets, or in closets. Smaller indoor bins can be made with materials you may already have. In addition to a bucket or container, you’ll need a drill, drill bits, and materials to make “worm bedding.” And of course, you’ll need worms.
I make indoor worm bins from Rubbermaid roughneck storage totes or five-gallon buckets. These materials are stackable, durable, and affordable.
I use two identical Rubbermaid roughneck storage totes (10-gallon minimum), and one lid:
That’s all it takes to make a do-it-yourself worm bin! To convert two five-gallon buckets into a worm bin, follow Steps 1 to 3, but place a brick inside the second bucket before completing Step 4. The brick creates a looser fit and will keep the two buckets separate over time.
Next, add worm bedding, a pound of worms, and feed.
Worm bedding can be made from carbon-rich materials like shredded paper, coconut husk, leaves, and wood chips. I mix several of these inputs with organic compost. To prepare the worm bedding, moisten the inputs as you mix them together. You don’t want the bedding material to be sopping wet. Imagine a sponge after it’s been rung out: it’s still moist, but not soaking wet. Once everything is well-incorporated and moistened, place it into the worm bin. I like to add a pound of worms throughout the filling process in layers. Make sure to leave a couple of inches for head space at the top to keep the conditions in the bin aerobic.
ARBICO Organics, Vermillion Wormery, and EcoGro are trusted local worm vendors.
Now, the moment we’ve all been waiting for: feeding our worms for the very first time. It’s critical that the food is buried a minimum of eight inches deep. A very common mistake is to throw food on the top of the worm bin or lightly bury the food near the top. This creates the conditions that fruit flies, fungus gnats, and cockroaches thrive in. Remember, bury the food! Wait for the worms to eat everything before feeding them again. Too much food in the worm bin will attract cockroaches and other undesirable bugs. If you’re using a five-gallon bucket as a worm bin, the food will be buried in the middle every time. Feeding worms in a rectangular storage tote is a little different. I mentally break up the storage tote worm bins into three sections. I like to rotate the feedings from left to right. This creates consistency in the quality of the worm castings throughout the entire rectangular bin, because we’re forcing the worms to move throughout it to feed and breed.
The most common question I get asked about raising worms is, “What do worms like to eat?” I mainly feed my worms banana peels, herbs, and grains—leftover oatmeal, quinoa, rice, tea bags, spent medicinal herbs, fruits, vegetables, and bread. Grains and herbs are important because worms require a high level of nutrition to be healthy and produce premium worm castings. Think of these two feed sources as worm superfoods. Any feed source that creates conditions where worms will clump up and rub against each other taps into their innate breeding behaviors. Banana peels do exactly this. They trigger breeding behavior in worms by enticing them to ball up. This is a great way to fill up your worm bin very quickly.
Avoid feeding your worms dairy products, meats, or high acidic or spicy food scraps (i.e. citrus, hot peppers, garlic, ginger, cinnamon).
At this point some of you may be thinking, “Can I just buy a worm bin?” Yes, of course! The tradeoff is the price, but these commercial units work very well. As a green professional, I’ve had hands-on experience with many of the commercially produced worm bins. Two worm bins that I would purchase for myself, family, or friends are the Worm Factory and the Worm Wigwam. The Worm Factory is ideal for backyard growers. A three-tray model runs around $80; find them at ARBICO Organics. If you’re more serious about worms, or want to produce worm castings on a community garden scale, then I’d recommend the Worm Wigwam, by Sustainable Agricultural Technologies. These units run around $650, plus shipping. A Worm Wigwam can process around 70 pounds of food and produce 55 pounds of usable worm castings a week, and will house more than 20 pounds of worms once it’s going strong. There are many products out there, but these two are the ones that give you the best value for the money
Building, or purchasing, a worm bin is a critical first step toward building up the soil food web. Let’s not forget that by feeding worms, we’re also taking care of the land—the soil beyond our yards. According to the U.S. Composting Council, 72 percent of the waste going to landfills is compostable. Think about that and ask yourself, “Do I have two unused buckets or storage totes?”
In the next issue, I’ll cover basic worm-bin maintenance, how to harvest worm castings, and how to build a compost tea brewer, a key tool for building our soil food web. ✜
Zotero Citlalcoatl is a permaculture designer and herbalist of the Sonoran Desert. Follow him on Instagram at @the_sonoran_desert_grower.