Project: Insulating a Worm Bin

I often joke that the worms  are my only pets, and to a degree, it’s true. I feed and care for the tiny red wigglers (Eisenia fetida) that live in bedding instead of in the ground and eat my kitchen scraps. This time of year, that means helping them stay warm on the coldest winter nights.

Here in Seattle, we often get our coldest weather in January, after which the Longest Spring on Record™ breaks bud in February. So I have to bring my garden through a month of cold. For the plants, that means an extra layer of floating row cover on the veggies that are surviving in the cold frames and cloches.

For the worms, that means insulating their box.

What to use

It’s as simple as wrapping the bin in some insulating material. You can use straw bales, bags of compost, or whatever you have sitting around that would keep out the cold.

I use half-inch expanded polystyrene (EPS) rigid insulation. It’s light, easy to work with, and provides just enough help. And it is weather-resistant, as it is rated for ground contact (used to insulate concrete) and to not retain moisture (used under the siding to wrap houses).

A 4-foot by 8-foot sheet is about $10, and can be cut to cover the sides and top of the worm bin.

worm-bin-insulation1

As the photo shows, it is covered on one side with a metallic facing material. On the white side, it has a clear plastic facing. Both surfaces are weather-resistant. I install it with the silver facing in, hoping that the heat radiating from the worm bin will be reflected back into the box. There are other types of EPS without the silver facing.

Cut and tape

I measure and cut pieces to be roughly the size of the four walls and the lid. The four wall pieces are held to the box with duct tape, which can be cut and left on the pieces when I remove them. Thus you can reuse the material many times.

Cutting this product can be a little messy. I use a sharp utility knife, but it still creates a ragged edge, because the material is made of tiny chunks of foam pressed together. No doubt a contractor would have a special tool for this, but it’s not worth it for my limited amount of use. Cut almost all the way through the material, then flip it over and carefully cut the facing on the other side. Clean up the foam bits that flake off.

The ragged edges will tend to flake off a bit more as you work with it and store it. For a cleaner look and more longevity, wrap the cut edge in duct tape.

The top is set on the lid of the box and held down with heavy objects. This makes it easy enough to feed the worms without having to tape anything to the wooden box, as the tape would either pull the paint off the box or leave residue behind.

worm-bin-insulation-slice

Two more tips

The worms have their own defensive reaction to the cold: they huddle together. In the winter I often find them in one warm mass in the center of the box. The collective heat will keep more of them alive. So to help your worms survive better in the winter, feed only rarely, and do it at the warmest point in the day. Dig a hole in the center of the bin and bury the food, covering it well.

Also, make sure the bin is completely full of bedding (leaves, straw, shredded newspaper, etc.). The bedding will also act as a great insulator.

bedded worm bin

The bedded worm bin, with a decaying pizza box to keep my plastic digging tool on top of the bedding.

Resources

If you’re just thinking of building a worm bin, check out the plans for a standard-size wood box (the one in my pictures) at the Seattle Tilth compost resources page. That section will educate you about compost, and there’s also a plan for an “off-the-shelf” worm bin that you can keep indoors.

For more details on caring for your squirmy pets, pick up a copy of Worms Eat My Garbage by Mary Appelhof.

 

Celebrating Soil

This morning, on the first day of spring, I took a walk through my garden, considering how to celebrate the occasion. One look at the planting bed I prepared yesterday gave me the answer: spring starts with the soil.

Garden Bed

The cleared soil is ready for planting if it’s warm enough, properly fertilized, and has no active plant decomposition.

Thsi time of year, much of my garden activity is amending, monitoring and making soil.

When I turn over a new bed, removing the weeds or straw mulch or chopping down the cover crop, I decide whether it needs to be amended. What did my soil test reveal about this bed? What did I plant in it last, and how did those plants do?

  • If the soil test showed the pH was low (meaning acidic, in our rainy maritime climate), I should amend it with agricultural lime.
  • If my last crop of lettuce in this bed did poorly, perhaps the nitrogen level was low, which is easily fixed with chopped cover crop or an organic fertilizer.
  • If my organic matter level was low (again, reading the soil test results) or I’m planning to grow a heavy-feeding crop, perhaps I should amend the soil with my home compost.

    Soil Thermometer

    A key tool for the cool-season gardener is a soil thermometer. This shows the soil in my newly worked bed is in the mid-40s, barely warm enough to sprout seeds.

Dry enough to plant?

If the soil is warm enough and dry enough, it’s ready for seeds.

Here’s an easy test to see how wet your soil is:

  1. Dig up a trowel-full, down to about 6 inches deep.
  2. Make a softball-sized ball with the soil.
  3. Toss that ball up in the air a few feet and let it fall on your open hand.

If the ball of soil breaks open in your hand, it’s ready to plant. If it hits with a plop and stays together with moisture oozing out, it’s still too wet.

Make and use your compost

I churned up the compost bin over the weekend with the first grass clippings.

To the moist, green clippings (rich in nitrogen) I added equal amounts of dry leaves, saved in bags from last fall. I mixed them together, watering well, and piled them in the bin.

Now, just three days later, they’ve heated up.

Compost Thermometer

Compost starts to aerobically decompose at 80 degrees F, which this bin reached in three days after mixing fresh lawn clippings with saved leaves and wetting it.

Home compost decomposes fastest when it’s in an aerobic condition, which means the soil decomposers have colonized the bin in great quantity and they’re busy breaking down the material.

Aerobic decomposition, or “hot composting,” starts at 80 degrees F., and look at what my compost thermometer shows!

When finished, my home compost will provide a valuable soil amendment that I can add to beds when planting.

It will be high in organic matter and contain a wide assortment of soil nutrients that will feed my plants, from macronutrients like N-P-K to the secondary nutrients like calcium to micronutrients like zinc.

What’s more, I’m creating that rich fertilizer for free, or at least for a very low cost of my own sweat equity, a couple of garden tools and a bit of water.

Home Composting

A 50/50 mix of greens (nitrogen) and browns (carbon) will decay into a nutrient-rich soil amendment, seen in the foreground.

The final step in soil building is to visit my worm bin. This is a closed box that contains a colony of “red wigglers,” a type of worm that specializes in decomposing kitchen scraps.

The worms live in bedding like leaves or shredded paper, and they’re fed vegetable and fruit trimmings from my kitchen (no meat, dairy or fats). Bacteria cause those scraps to decay, and the worms eat the bacteria, pooping out a “vermicompost” that’s even richer than the stuff in the home compost bin.

Worm Bin Composting

Partially decaded vegetable matter is wet and slimy. The red wiggler worms (Eisinia foetida) eat the decayed material, and their castings make a soil amendment richer than compost.

It’s another nearly free form of soil amendment that helps me close the loop on my home waste stream and use less externally purchased amendments in my garden.

As I get ready to plant, my prepared garden bed will get a good dose of worm compost or home compost dug into the soil, or sprinkled into the planting hole where the transplants will go.

On this first day of spring, the best thing I can do to honor my garden is to turn my attention to the soil.