Elizabeth Smith’s house is quietly unassuming, tucked among rows of nearly identical houses in southeast Tucson’s Rita Ranch. But in her backyard, buried under a layer of mulch, is a gardener’s treasure—beds full of dark soil, teeming with home-grown earthworms.
Smith, a solar power consultant and avid gardener, says that her earthworms act as a miniature soil factory, gobbling up fruit peels and vegetable shavings and turning them into rich soil. Her garden is a prototype for a community garden that she is helping to plan in the neighborhood’s Purple Heart Park. Between showing me her citrus trees, her leafy winter greens, and the giant ceramic pot in which she collects rainwater, she explained to me how she borrows tricks from nature to add nutrients into her soil, use water efficiently, and keep her garden thriving.
How long does it take your vegetable compost to turn into soil?
I’ll start by digging a hole to bury my compost around the base of a tree. It’ll take me maybe four to five weeks to make my way all the way around tree. By the time I get all the way around, it’ll be decomposed. It’ll be soil. You can’t even tell it used to be banana peels in there.
And you put the earthworms in with the compost to speed up the process?
Right. The earthworms and the microbes get in there and break it down for me. Their excrement is called vermicompost, or earthworm castings. Earthworms will break down all that carbon in compost a lot quicker and turn it into fertilizer. My fertilizer is very high in nitrogen. You can do it without earthworms, but it won’t happen as quickly, and you won’t have as much nitrogen introduced.
How long have you been raising earthworms?
We first did this as a project when my son was in fourth grade, about 20 years ago. I got them from a friend in Rita Ranch who’s had them for years and years.
Smith pries the lid off a bucket, one of the shelters in which she feeds and nurtures worms. She fumbles among the chunks of squash compost, clusters of dead leaves, and soil within, and unearths several fat pink earthworms. There are tens, maybe hundreds of tiny white worms, barely thicker than a human hair, wriggling alongside their adult counterparts.
Whoa! That’s super cool.
They’re real happy—they’re makin’ babies! Right here there’s never any direct sun, so this is a good place for them.
What do you feed them?
Carbon and nitrogen—you need the right ratio. Carbon-rich matter is usually brown: dry wood chips, shredded toilet-paper rolls, dry leaves. Nitrogen-rich matter is all the fresh stuff, like salad greens, apple cores, potato peelings, banana and citrus peels. If it was all fresh stuff, it would rot.
What other techniques do you use to compost to soil?
It also helps to have a layer of mulch over the top of the bed so that it stays moist. A lot of people have these plastic drums for their compost, which just stays mummified for months because it’s so dry here. Mulch is super, super important in the desert. It holds the moisture in—it actually self-regulates the moisture. If there’s been a lot of rain, the water just filters through it naturally. If it’s been dry, the mulch will hold onto it.
There are two things going on: the rich, dark soil absorbs the water like a sponge, and the mulch protects it like a blanket. I refill the mulch about once or twice a year.
Mulch is protective too, right?
It protects the roots. Because I’ve got so much mulch and compost in here, the root system is huge. You have a stronger, healthier plant. It can withstand a lot more. If one of my pepper plants gets frozen, the mulch protects it from dying off completely. It’ll come back bigger in the spring.
Smith shows me her greens—verdant kale, chard, beets, and various herbs. Because of invading roots from a neighbor’s eucalyptus tree, she keeps these plants in pots that are buried in the garden bed.
So how much water does your garden need?
In the summertime, I’ll water the trees maybe once every couple weeks. In the wintertime, they can go easily over a month without watering. The mulched vegetable beds can go up to a week without watering in the summertime and much longer in the winter because of the permaculture method I use. I check the moisture level of my earthworm bin about once a week. They just need a quick sprinkle when I do add water to them.
The roots are getting what they need, so the plants are hardy and strong. I never have to shade anything. But I don’t try to plant orchids or plants that won’t survive here no matter what I do.
I learned this earthworm method from a guy in Seattle who has a YouTube video on it called “Back to Eden Organic Gardening.”
Why do you like gardening?
I just feel connected to the earth and the soil. And how one little seed could feed the entire world—I love that exponential gift. ✜
Sophia Chen is a freelance writer based in Tucson. Her work has been featured in Wired and Physics World.