Making Your Own Worm Bin

Tuesday, August 23, 2011

Earth worms are an essential part of good gardening. At least in my mind they are. They are eating machines, transforming kitchen and garden scraps into nutrient rich soil and castings, while churning up the soil, aerating it and improving its tilth.

Raising your own earth worms is easy and inexpensive, if you use materials you already have on hand. Or, you can buy a worm bin system from a garden center or by mail. But, no matter how you come to raising earth worms you’ll never regret the initial work or cost and your garden will benefit greatly from the improved soil.

I was lucky – the previous owners of my farm left a multi-tiered worm bin when they moved out. It sits in the shade near the barn with easy access to the garden and rabbit hutches, and is used all year round. The soil produced is a great addition to our raised beds, as long as I can keep the chickens from eating the worms. But, that’s another story.

To build your own worm bin all you need is a container, either a wooden box, plastic storage bin or 5-gallon bucket. Any type of container should be about 18 to 20-inches deep, but no more than 24-inches deep.

Ventilation of the bin is very important, so which ever type of container you choose drill a few dozen ¼-inch holes in the top and 1/8-inch holes in the bottom and on the sides so the water can drain out. If you purchase a worm bin system they will have a mesh looking bottom for ventilation.

The bin should also have a top or cover to keep out the light and to keep the soil from drying out. Worms like a dark, moist living space. Solid tops should have vent holes, or you can use a piece of burlap which allows you to water right through it.

Once your bin is made you’re ready to prepare it for the worms. Fill the bin about 3/4’s with shredded newspaper, straw, dry grass, peat moss or a similar material. This bottom layer will give the worms a source of fiber and keep the bin well ventilated. Next, sprinkle a few handfuls of dirt on top of the fiber material and thoroughly moisten everything. Let the water sit for a day before putting in the worms. If there is too much water, simply pour some off. You don’t want it to be soaking wet, only moist.

After the bin has sat for a day you’re ready to add the worms. There are several ways you can get worms; buy them off the internet or from a garden center or gardening club. Digging worms from your own yard is not normally recommended because they can be non-native worms that if let loose can upend the natural balance of your area. But, since I am basically breeding worms for my garden beds I want native worms that are accustom to my soil and climate, so I prefer digging my own. You decide which route you want to take.

If you decide to buy worms, the most common varieties are the Red Wigglers and the European Night Crawlers. Night Crawlers don’t reproduce as quickly as Red Wigglers, but they do grow larger, which makes them an ideal fishing worm (if people still fish with worms rather than using Power Bait). They can eat coarser paper and seem to be heartier than the red wigglers. My worms seem to be a version of the Night Crawler because they are big and fat when full grown.

When the bin is fully set up it will need to be maintained. Keeping the bin off the ground will speed up the composting. Use blocks or wood to set the bin on. To keep the soil moist and the worms happy, sprinkle the bin with water every other day. Worms should be fed at least once a week. Feeding small amounts every day though will produce more worms. Add your fibrous material like hay, straw or paper once a month. Worms move through the materials quickly, so when the bin is half composted refill it with your fibrous material and food.

If you’re using your bin as a composter there are a couple of ways to harvest the final product. Because I am using my worms in the garden I do things a little differently, which I’ll explain in a minute. Move any large uneaten vegetables to one side of the bin. Gently scoop up some of the worms with their compost and set them on a brightly lit piece of paper. Now scrap off a layer of compost, allowing time for the remaining worms to burrow down to the center of the bin. The goal is to end up with a pile of compost next to a pile of worms. Remove the compost and use in the garden or containers, replace the bedding, and return the worms to the bin. If this sound too time consuming to you, you can simply move the soil and worms to one side and refill the empty side with paper, soil and vegetable scraps. The worms will eventually migrate to the new pile.

When I harvest from my bin I move some of the compost and the worms to a raised vegetable bed. I loosen the soil and dig a hole before placing the compost and worms in the hole. After a few minutes the worms begin to burrow down into the bed. I gently recover the hole and let the worms compost and reproduce naturally.

Here are a few tips to make your worm bin as productive as possible.

• Raw, not cooked, egg shells will add calcium to your bin. To get the most benefit, dry and crush egg shells with a rolling pin before putting them in the bin.
• Throw coffee grounds, tea bags and unbleached filters right into the bin. But, remember to take out the staples.
• Worms will move through chopped food much faster than whole.
• If you want to collect the liquid fertilizer from the raised bin, simply place a collection try under the bin. The nutrient rich water can be used on potted plants or in the garden.
• Green foods like green grass, beet tops, carrot tops, fresh cut clover or alfalfa increases nitrogen.
• Brown foods like paper, cardboard, wood chips, leaves, bread increases carbon and phosphate.


• Don’t put meat, dairy products, eggs, or oily foods into the bin.
• Go easy on the citrus rinds, they are an acid and can affect the balance of the bin.
• Don’t allow your bin to dry out, they will die without water.
• Worms can’t handle extremes in temperature – about 50 to 80 degrees Fahrenheit is ideal. Outside bins should be kept in the shade.
• Don’t allow your worm bin to heat up past 90 degrees, they will cook and die.
• Large amounts of greens like grass, alfalfa, etc. should be added lightly because it heats up the bin.
• NEVER use fresh uncomposted manure. It has harmful pathogens that can heat up the bin or kill the worms with deadly levels of bacteria.

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