By Stephen Ulman

The UN Food and Agriculture Organization has declared 2015 as the International Year of Soils, so AUA will be bringing you soil-related resources throughout the year. To start off this winter right, consider creating a worm bin in your home. 

Right now is a great time to start a worm bin. The depths of the winter doldrums may be upon us, but deep beneath the blankets of snow and frozen soil, life goes on. Soil-building is a year round activity, and by employing the help of some industrious little worms called red wigglers (Eisenia fetida) you can create rich organic compost called vermicast that is great for new seedlings or amending existing pots and beds.

Best of all, a worm bin doesn’t have to take up much room and kits are readily available. Worm bins come in many shapes and sizes, but they all have a few things in common. Worms like it dark and moist, but not too wet. They are voracious eaters and can consume a variety of organic materials. If you have cardboard and vegetable scraps, you can make a worm bin.

A discreet home composting system complete with a tight fitting lid and ventilation holes.

A discreet home composting system complete with a tight fitting lid and ventilation holes.

Your bin should either have drainage holes, or you must be vigilant that it does not get too wet. A secure fitting lid is also necessary to reign in any wanderlust your new pets may have. Determining the size of your bin depends on how much waste you and your household produces, and how much vermicast you want to create. A worm can eat half its body weight daily. So, if you have a pound of worms, you will need to supply half a pound of food a day to your worms. Fortunately, worms are not picky eaters. They will eat just about anything organic, including cardboard, newspaper, and cotton t-shirts. These items take a while to break down, so they are useful as bedding for your worm bin.

For a new bin, you will want to make a nice spongy layer of soaked paper or cardboard (or both) that has been wrung out and ripped into strips or pieces. Adding some outdoor soil will introduce both beneficial microbes and some grit to aid the worms’ digestion. Next, bury in the bedding a variety of food as some things break down faster than others. Coffee grounds, for example, will be quickly consumed. If you add whole fruits or vegetables, make sure to puncture the skin or cut them into smaller pieces, otherwise the worms will not be able to penetrate them until they further decompose. Now, add your worms and cover them with more bedding or a damp piece of cloth to create a barrier that will help retain moisture and keep out flies.

Do not feed your worms any meat, dairy, oils, or pet feces. This is a health risk because your bin will not get hot enough to kill potentially dangerous pathogens. Also avoid adding too many citrus rinds or spicy peppers because they contain compounds that are natural pesticides. Once these break down, however, your worms will voraciously consume them.

Observation is essential for maintaining a worm bin. Check in on your new friends every couple of days to make sure conditions are favorable. Refrain from adding water or food if things look too wet or there are many uneaten scraps. Your worms will eventually reach a stable population relative to the size of your bin and availability of food.

On average, a worm bin takes about 90 days before it is ready to harvest, which will be just in time for spring planting if you get started now. Obviously, a smaller bin will require harvesting sooner than a larger one. If you notice a spike in the number of escape attempts, it may be time to harvest. There are several methods, but the goal is to separate the worms from their castings. I like to harvest my bin a little at a time, picking out worms and undigested food and putting them back in the bin.

If you’re ready to put worms to work for you, check out these resources that can explain things more in depth.

“Composting with Worms,” Oregon State University:

“Herman the Worm,” University of Illinois Extengion:

Nature’s Little Recyclers Mini Worm Bins:

AUA welcomes blog contributions from Chicago’s diverse urban agriculture community, including AUA members and non-members alike. Since AUA is a coalition of individuals, organizations and businesses that strives to represent the broad interests of it constituency in a democratic and transparent manner, it is important to note that the views expressed on the AUA Blog do not necessarily represent those officially endorsed by AUA.