How to compost with worms

Worms may be creepy, wiggly little things, but they benefit lawns and gardens by aerating the soil and recycling kitchen scraps into rich, organic fertilizer.

As worms crawl in and out of soil, they aerate it as well as pick up and transfer nutrients, said Angela Adams, a University of Arizona master gardener who raises her own worms in terra cotta pot bins. If you have garden beds in shaded areas with worms, you can add kitchen scraps to “create little worm delicatessens to keep them happy,” she said.

They will eat the scraps, break down the organic matter in their systems and poop it out.Worm poop, called worm castings, is rich in nitrogen and other nutrients, she said.

You can also raise worms in bins and harvest the castings.

“In about six to eight months, you’ll have castings,” said Michael Rosner, worm farmer and UA master gardener. “Castings look like little, fine coffee grounds. That’s the actual compost, the end product.

“You can spread out a thin layer, a quarter-inch or so, around plants."

Raising worms in bins is easy, he said. “They’re very low maintenance.”

If you don’t have the time or the inclination to farm worms yourself, you can buy packaged castings from Rosner’s Li’l Known Worm Farm, 920-8469. But if you’re game, Rosner has provided some easy steps you can follow to create your own mini worm farm.

Although various wooden, plastic or terra cotta containers can be used for worm bins, the following instructions are for a whiskey barrel bin for farming red worms.

Because worms multiply over time, Rosner recommends starting out with a half-pound of worms for the whiskey barrel (a pound for larger bins and a quarter-pound for smaller bins). You can purchase them at local bait shops, hardware stores or from Rosner.

As the worms multiply, some will naturally die off. But in the fall, you can thin out the survivors by placing them in your lawn and garden beds, where they will work the soil, adding nutrients as well as air pockets that promote root growth, he said.

Materials needed

- Wooden whiskey barrel planter

- Peat moss

- Moisture gauge

- Composting rod with temperature meter

- A few scoops of sand

- Kitchen scraps (no meat or bones)

- 1 pound of red worms

Steps for creating a worm bin

Add worms to bin after creating bed and adding scraps.

1. Bedding - Make bedding by loosely spreading 12 inches of peat moss in the bottom of the whiskey barrel (above). (Moisten the peat moss by wetting it and squeezing out excess water.)

2. Kitchen scraps and sand - Pull back a few inches of the top of the bedding with one hand, and add kitchen scraps with the other. You can use kitchen scraps such as coffee and tea grounds, vegetables and fruits. You can even add shredded paper. But animal products are not recommended because they attract varmints and make the bins stink.

Worms need grit for their gizzards to function properly, so add a few scoops of sand to the bedding as well. Cover the kitchen scraps and sand with the top layer of bedding.

3. Shade - Always keep the worm bin in a shady area.

4. Moisture and temp. - Keep worm bedding moist, “like a wrung-out sponge.” Probe the bedding with a moisture gauge, which rates moisture. If the moisture is in the middle range, it’s fine. If it’s dry, add a little water.

Check for moisture about once a week during cooler months and more frequently in summer. If it’s too wet or too dry, the worms will be in distress.

The ideal temperature range for red worms is between 55 and 77 degrees. Use a composting rod with a temperature meter to check the bedding temperature daily.

During the summer, moisture evaporates from the bedding, cooling the bin much like an evaporative cooler would. But Yuma summers can get a bit warm for worms, so some people keep their bins inside. If you do, be aware that the bins may begin to stink if they are too moist. (Because Rosner is a worm farmer with several bins, he keeps his in a separate, small building, which he cools with an evaporative cooler during the hot months.)

5. Feeding - Feed your worms kitchen scraps about every other day. (The amount of worms and kitchen scraps can vary from one household to another, so lift the top layer of moss to see if worms have scraps or need some.)

6. Drainage, air circulation - Worm bins need proper drainage and air circulation. You can provide both by drilling small holes in the bottom of the container. (For containers with lids, drill holes in the lids as well).

7. Caution - Pesticides will kill worms, so use with extreme caution and away from your worm bins. If you want to keep worms in garden beds, an organic, non-toxic pesticide may be the best choice.

Additional information

For more info on composting with worms, call Rosner at 920-8469. As a UA master gardener, he may also be able to help you with any gardening questions.