Clippings
A Weekly Column about Plants, Gardens, & Yards
By: Margaret Murphy • ISU Extension Horticulture Educator • Lyon-O’Brien-Osceola-Sioux Counties
For the Week of October 22, 2012
Composting with Worms
Backyard composting is an excellent way to recycle yard and kitchen waste during the growing season.
But what about the kitchen scraps we generate through the winter months? Why not let worms eat your
garbage? Known as vermicomposting, composting with worms is an excellent way to turn those scraps into
nutrient-rich compost that can be added to your garden or flower pots next spring.
To get started, you’ll need worms. Red wigglers are considered the best for composting. They
reproduce quickly and adapt well to life in a compost bin. European night crawlers will also work. I compost
using them. Do not use earthworms or night crawlers that you find in the backyard after a hard rain. These
types of worms are not well-suited to living in a container and will not stay alive. Composting worms are
usually available at local bait shops and can be ordered from numerous places online.
So, how many worms do you need to get started? Well, a starter colony is typically a pound of worms,
which equals approximately 1,000 wigglers. The actual amount of worms needed depends on how much
kitchen waste you will be adding to the bin. A pound of red wigglers can consume roughly ½ pound of food
scraps per day. Keep in mind, however, the worms will begin to multiply on their own. If you maintain the
right environment for your worms, you’ll soon notice eggs and immature worms in the bin together with the
adults leaving you with a continual supply of composters.
To determine the appropriate bin size for your needs, you must first figure out the amount of surface
space required. The rule of thumb is 1 square foot of surface area for each pound of waste. So for example, if
your household generates about 6 lbs of compostable food waste per week start with a bin that is 2’ wide x 3’
long. The container doesn’t have to be very deep, 10 to 12 inches is fine. Red wigglers are shallow burrowers
and feed in the upper layers. You can buy a commercial worm bin or make your own. Plastic totes are
commonly used. If you make your own bin, you’ll need to provide air holes. Drill holes a ¼ inch or smaller into
the sides and the lid.
It’s important to keep the bin in a place that will not get too cold or too hot for the worms. Red
wigglers prefer temperatures between 55 and 77 degrees F. The bedding material should never freeze or
become hotter than 84 degrees F. I keep my bin in the basement but a heated garage will also work. If the
weather outside is moderate (between 55 and 80) the bin can be placed outside in a shady area alongside the
house or garage. Worms are sensitive to light so make sure the bin is covered.
It’s important to put proper bedding in the bin. Worms breathe through their skin so the bedding must
hold moisture and allow for air circulation. The bedding will be consumed along with the food scraps so it also
needs to be biodegradable and non-toxic to worms. Materials that work well include shredded newspaper (no
shiny print), shredded computer paper, or old leaves. Wet down the bedding and wring out any excess water.
Too much water can drown your worms. Fill the bin about 2/3 full with the fluffed bedding and add a shovelful
of garden soil to supply grit for the worms’ digestion. Now you are ready to add the worms.
Start adding food gradually until you see how fast it disappears and then adjust the amount
accordingly. Feeding the worms once a week is usually sufficient. Acceptable food includes small scraps of
vegetables and fruits, coffee grounds and filters, tea leaves and bags, bread, grains, and crushed egg shells
(they also provide grit for the worms). Do not put in any meat, fish or dairy products, or oily foods.
Worms are master composters. They can turn your food waste into rich, dark compost and worm
castings in 3 to 5 months. Harvest the compost about 2 to 3 times a year. To make scooping the compost
easier, harvest under a bright light as the worms will migrate toward the bottom of the bin to avoid the light.
You can also do the “dump and sort” method. Dump the bin out on a tarp and create several small piles. Wait
for the worms to move into the center of the pile. Remove the compost until you reach the worms and then
return them to the bin along with any eggs. Refill the bin with fresh layers of moisten bedding and food when
finished.
Vermicomposting is a great winter project and one that can get kids involved with composting and
recycling. For more information on vermicomposting, feel free to contact me at mmurphy@iastate.edu, by
phone at (712) 754-3648 or through your local County Extension office. Additional information was provided
by the following publications: Clemson Cooperative Extension, Worm Composting, Oklahoma Cooperative
Extension Service, Vermicomposting-Composting with Worms, Texas AgriLife Extension Service, Vermiculture:
Worm Composting, and the University of Nebraska-Lincoln Extension, Vermicomposting: Composting with
Worms.
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