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Master Gardener Journal  


S P E C I A L   F E A T U R E



Worming Your Way to Fertile Ground

by Janet Beaver, Master Gardener Intern

Tired of running all the way out to your compost pile with your vegetable scraps? Looking for a fun ecology project for your kids? Interested in trying your hand at composting, but your yard has always seemed too small? If you answered yes to any of these questions, consider trying 'vermicomposting' or worm composting.

Creating a worm bin and managing worms for composting is an easy activity to become involved in, and results in rich organic material to add to your garden. Less material is wasted and dumped in landfills, and you'll have a new subject to astound your friends with at the next cocktail party. The basic requirements for composting with worms are food; a container; the correct temperature; moisture and light; and a quiet, convenient location for your bin and WORMS!

Begin by quantifying the amount of food you will have available for your worms to eat each week. This information will determine bin size and the number of worms you will need. The worms used in vermicomposting eat mainly kitchen wastes. Vegetable and fruit wastes, as well as coffee and tea grounds are acceptable food sources for the worms. Just as with a regular compost pile, meats, fats and oils, pet wastes, and non-biodegradable products should not go into your worm bin. Save your scraps for a week, and then weigh them. Divide this weight by 7 (for 7 days of the week) to get a figure for the Average Weight of available food for your worms each day. Multiplying the Average Weight by 2 will give you the weight in worms you will need for your bin.

Example: At the end of the week you have 3.5 pounds of kitchen waste. Dividing 3.5 by 7 equals .5 pounds of waste each day. Now multiply .5 times 2 to equal 1. You would need 1 pound of worms for your bin. The number of total pounds of scraps per week is also the minimum number of square feet you need for the size of your worm bin. In our example the bin should have at least 3.5 square feet of space.

Worm bins range from simple wooden boxes you can construct yourself and plastic containers you can easily modify, to elaborate commercially produced systems that cost several hundred dollars. Whatever the design, the bin should have good ventilation and drainage. There are examples of bins available at the websites listed at the end of this article.

Once the bin is made, you will need to create a comfortable bed for your worms. Shredded newspaper, straw, sawdust, or brown dry leaves are all suitable materials for the bed, as they retain moisture, provide cover from light, aide in ventilation, and can be consumed by the worms. A little sand or topsoil can also be added.

The bedding will need to be watered until just moist. Worms require a 75 to 90 percent moisture content, or 3 parts water for every part of dry bedding. To determine if you have the right moisture content, pick up a hand full of bedding and squeeze. Just a few drops of water should come out; any more than that and you have over watered your bedding.

Location, location, location is as important to worms as it is to us. You need to find a location for your worm bin that will be convenient for you to use, provide shelter from bright light (even though your bin will probably have a lid on it), allow you to maintain a temperature range of 68 to 90 degrees Fahrenheit, and will not be kicked or jostled. If maintained properly the worm bin will not smell, so an indoor location is fine. A utility room, the kitchen (some people suggest under the sink), the garage or carport, a spare bedroom, or a cool, covered patio can be good places for your bin. Once you know where you are going to place your worm house, you are ready to introduce your worms.

The best worms to use for vermicomposting are the Red Worm, Eisenia fetida (I have seen this spelled Eisinia fotida and Eisenia foetida). These worms have proven to be successful because they feed on the surface of organic materials (great for eating up those apple cores) and can survive in the confines of a bin. The easiest way to obtain worms (unless you are lucky enough to know someone who already has a worm bin and wants to share) is to mail order them. There are many companies that supply worms; a quick Internet search will turn up many choices. Some of the websites given below offer suggestions on obtaining worms.

Feeding your worms is easy. It is suggested that scraps be chopped up a bit to speed the composting process. You may even want to whip your materials in a blender before feeding them to the worms. It is best to alter feeding locations within the bin, and to bury the food rather than leave it on top of the bed since worms prefer to live away from light. To avoid a fruit fly infestation, first place your materials in the freezer to destroy any eggs that might hatch. Depending on your bin's conditions and the water content of the food you use, you may not have to water your bin. Keep in mind the 3:1 ratio and add water if needed.

If you feed and water your worms adequately, in 4 to 6 months you will be rewarded with a compost of worm "castings" (a polite word for fecal matter). These castings can be added to your garden just like your other compost, or used as top dressing for indoor plants. The castings are rich in nutrients and improve soil aeration and drainage.

I was introduced to worm composting when living in Washington State. Most of the reference sources I found were located in the Pacific Northwest and other more humid parts of the country. From my experience in Phoenix, I can offer a few further suggestions:

If you choose to keep your bin outside, DO NOT bring it inside. I kept my bin on a north-facing covered patio. One night last winter when threatened with freezing temperatures, I decided to bring my bin inside to save my worms from freezing. I woke up the next morning and found many uninvited flying guests in my living room. I moved the bin back outside and spent a week getting rid of the unwanted guests. The worms would probably have been fine with just a sheet of plastic and blanket thrown over them.

My worms seemed to do fine in temperatures from the 40s into the 90s, but my biggest problem was moisture retention. I was using a plastic bin system, and had to constantly monitor it so it did not become too wet or too dry. The bin would quickly dry out in our low humidity and high summer temperatures, but I had to be careful to not flood the poor worms either. Misting seemed to help.

If you leave your home for more than 4 days, you must have someone take care of your worms. I lost mine after a 10-day leave of absence due to lack of moisture.

I made my bin following instructions by Klickitat County. It's an easy project to complete and only requires three Rubbermaid-type tubs, a little wire mesh and a drill. To view the instructions, go to: www.klickitatcounty.org/solidwaste.

References
Blair, Jay. "Black Gold: Vermiculture on the Modern Homestead." Countryside and Small Stock Journal. Sept/Oct 2001 Vol 85 #5. On-line. MasterFILE Premier. January 29, 2003.

Paley, Brian. "Vermicomposting: A Vermicomposting Primer." June 23, 2001. www.gnv.fdt.net/~windle/primer.htm

Savonen, Carol. "Worms: Let Worms Turn Your Food Scraps Into Beautiful Compost." Gardening Information, Oregon State University Extension and Experiment Station Communications. January 29, 2003. www.eesc.orst.edu

"Composting With Worms." Stewardship Gardening, Washington State Cooperative Extension. January 29, 2001. www.gardening.wsu.edu

"The Art of Vermicomposting." Frankel, S. Zorba, Editor. Worm Digest. September 2001. www.wormdigest.com


Maricopa County Master Gardener Volunteer Information
Last Updated July 28, 2003
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092