This article is the second in a series on Vermicomposting. See article one here and article three here. If you’re interested in exploring other techniques for creating rich compost, check out our class on Homestead Scale Composting with Noah Sanders from Redeeming the Dirt.

Why Climate Matters More in Vermicomposting Than Most People Expect

We discussed in our first article in the series that red wigglers have a tight range of preferred soil temperatures – between 55°F and 77°F (12–25ᐤC). They can tolerate up to 90°F (12–32ᐤC), but once the bin gets too hot or too cold for an extended period, the worms slow down, stop eating, and eventually die. And since most people don’t account for the fact that the soil inside an active bin tends to run 10ᐤF to 20ᐤF (5.5–11ᐤC) warmer than the surrounding air, your worms can get uncomfortable fast on a day that you find perfectly pleasant.

The good news? Most climates are workable, and all it takes is a little observation and planning.

If You Live in a Hot or Arid Climate

Heat is a worm's biggest enemy. In dry, hot, or subtropical environments, there are a few things you can do to keep your worms cool and happy. 

Keep the bin in the shade. Your first priority is to get your worm bin into the shade for most, if not all, of the day. Place the bin on the north or east side (if you’re in the Northern Hemisphere) of a building, fence, or tree line so it receives shade during the hottest part of the afternoon. Avoid spots where the bin will sit in full sun even for a few hours. A shaded patio, the cool side of a barn, or a covered outdoor area all work well.

Bury the bin partway into the ground. The soil temperature below the frost line stays relatively stable year-round. Sinking the bin several inches into the earth lets the ground act as insulation and keeps the bin cooler, similar to the spring houses of yore that kept food from spoiling during the summer.

Cover the bin to keep out heat. In extreme heat, the cover matters, too. A thick, solid plywood lid insulates the bin better than a plastic lid, keeping the interior cooler and more moist. Make sure the cover still allows some airflow, but don't leave the bin exposed during a heat wave.

Check the moisture frequently. If you have a stretch of hot weather, you'll want to check moisture more frequently. Heat pulls moisture out of the bedding faster than the worms can work with it, and a dry bin is almost as bad as an overheated one. Check the bedding every few days rather than weekly and mist lightly with chlorine-free water as needed to keep it feeling like a damp, wrung-out sponge. If you’re not sure how to source chlorine-free water and missed our first post on setting up a worm bin, it’s worth a quick look to understand the ways you can make your water work for your worms. 

Add bedding or increase the bin size. Larger bins hold temperature more steadily than small ones, so whether you live somewhere consistently hot or cold, err on the side of a bigger container. For cold climates, the dual advantage of a larger bin is that more mass will generate more heat, like a larger compost pile. 

Let’s turn now to strategies for climatizing your worm bin for a cold region.

If You Live in a Cold or Northern Climate

Cold slows worms down, but it doesn't necessarily kill them — as long as you manage the transition carefully. Worm cocoons are more cold-hardy than adult worms and can survive temperatures that would kill the active population. Even so, the goal is to keep the bin active rather than letting it freeze.

Here are a few approaches, from least to most intensive, many of which can be combined for greater effect:

Add more bedding. A thicker layer of carbon-rich material insulates the bin from temperature swings. Before the cold sets in, pile in extra shredded cardboard, wood chips, or leaf mulch. The deeper the bedding, the more stable the soil temperature stays. Worms will burrow down into the warmest layer and keep working.

Cover the bin with a blanket. A moving blanket or even a tarp could work well to create an extra barrier against the cold air and better insulate your worms.

Bury the bin partway into the ground. This strategy is also recommended for hot climates and works especially well with larger bins.

Move the bin indoors. A garage, shed, mudroom, or basement that stays above freezing is enough to keep a worm bin active through winter. A well-maintained bin doesn't smell, so bringing it inside is a practical option for many homesteaders. The worms may slow down and eat less in a cool space, but at least they’ll survive.

Use a seedling heat mat. For small bins or bins in unheated spaces that dip below freezing, placing the container on a seedling heat mat can raise the soil temperature just enough to keep the worms active. It's a low-cost option that works well for a single tote-style bin.

Year-Round Habits That Help

Regardless of climate, a few consistent habits make the bin more resilient to seasonal changes.

Keep an eye on moisture. Both heat and cold affect how fast the bedding dries out or stays wet, so adjust your watering habits accordingly. In winter, you'll likely add less water, and in summer, more.

Feed smaller amounts more consistently rather than large amounts infrequently. An overloaded bin not only attracts unwelcome insects, but it generates heat as scraps break down, which can push a summer bin past its limit. In winter, smaller amounts are easier for a reduced (and less active) population to process.

Assess the bin’s placement over time. Where the bin sits in March may not be the right spot for it in July. Notice the movement of sunny and shady spots across your property, so you can avoid leaving your worms in a heat trap come summer or a frost pocket during the winter. Moving the bin seasonally — even just a few feet — can make a real difference in how well it performs throughout the year and can prevent temperature-related problems. 

Worms are forgiving livestock. With a little attention to their environment, a well-sited bin can keep producing castings in just about any climate.

One More Thing

Keeping worms can be beautifully simple. Our job is to steward the vermicompost system so that it stays healthy and prolific. With a little observation and the occasional adjustment, you can help your worms thrive despite hot summers or cold winters and keep them at (or close to) peak productivity. 

What does a thriving worm bin look like? It means a worm bin that can generate castings in as little as eight weeks. That’s several cubic feet of high-quality compost with minimal time and money invested. 

But how do you know when the castings are ready to harvest, and how do you apply them effectively in the garden? These questions – and more! – will be tackled in our next article in this vermicompost series, so be sure to check that out.

If you’re excited about all the benefits of compost and have the space outside to do it, consider creating a large thermal compost pile in addition to your vermicompost bin. Each strategy has its own strengths, and many homesteads of all sizes have chosen to use both systems. Why? Because they can handle larger volumes of waste, provide for all their garden fertilizer needs, and enjoy access to a source of winter protein for their chickens – fresh worms from the bin.

To get started with outdoor thermal composting, explore the Homestead Scale Composting Class with Noah Sanders. Over a decade ago, Noah Sanders wrote a book that spawned a movement, and since then, he has taught this method to thousands of people in hands-on classes and demonstrations. But through his class at the School of Traditional Skills, you can learn how to build compost that feeds your soil and helps your garden flourish from the comfort of your own living room!