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Worms and Vermicompost

Worms are valuable critters.  In addition to improving soil chemically with their castings, worms improve soil physically by opening airways and drainage holes as they travel.

Worm castings are a mixture of their manure and the slime emitted through the worms’ skin.  It is called vermicompost, and is very rich in plant nutrients.    Studies have shown that when only 10 percent of the volume of soil used to grow plants is vermicompost, plants grow better.  And studies have shown that small amounts mixed into soil suppress diseases, slugs and insects.

Vermicompost can be made by enticing worms to you garden habitat.  They will emit it naturally.  Or you can create vermicompost in bins.

Worms in your Garden    Available organic matter is the key to building up worm populations, but it may take awhile; their time from cocoon to maturity is four-12 months.

Hopefully you already have worms in your ecosystem.  But they will not stick around unless the soil is moist and rich in organic matter.  Many worms dig deep into the soil as the weather heats up in summer. Dotting the garden with piles of moist organic matter that are shaded by tall plants is an easy way to keep worms up in the root zone in hot weather.

Keep a layer of decomposing litter at your garden’s surface. Make sure the soil is moist and rich in organic matter. Dig in compost between plantings and add heavy mulching.   Night crawlers are valuable for soil fertility  They will build semi permanent burrows, where they stockpile food gathered at night.

Place wet newspapers or cardboard over the surface of soil to provide shelter for worms.  Sprinkle raw oatmeal over the newspapers.  This is food they like.  Top with 2 inches of coarse, moist compost. Repeat the layers and top off with grass clippings, straw or another attractive mulch.

Or build a slowly rotting compost pile. Worms often build deep, elaborate burrows beneath piles of slow compost.  Or simply let a pile of old hay rot. Worms love decomposing hay.

Making Vermicompost in Bins

Night crawlers like to burrow, so they are only marginally happy in bins. Common red worms or field worms do fine in bins.  You will need about a pound of worms to start a worm bin. These worms transform a mixture of bedding and food into finished worm compost in about four months.

To make a bin, choose a dark, cool place such as a basement or remote closet where temperatures range between 50 and 65 degrees.

Use modest-sized plastic storage bins or Styrofoam coolers.  Use dark-colored containers to reduce the light, or cover clear containers to block out light.  For 3-4 pounds of scraps per week, your bin should be at least 2 feet square.  Make several holes in the side of each bin for air flow.

To create the environment inside the bin, soak cardboard, newspaper or other paper in water, and then tear it into ragged 3-inch pieces. Mix with 1 gallon of compost or soil.  Don’t use sand or sandy soil, because sharp sand particles are abrasive to soft-bodied worms. Let the mix sit for a day or two.  Then add a pound of worms.

Feed your worms grains first.  They will like that grains decompose so quickly.  Old bread, or cooked rice or cereal is ideal.  Bury it in small batches just beneath the top surface of the paper.  In a few days, start feeding worms kitchen waste.  Wait until the buried food disappears to add more.  Keep the bedding uniformly moist.

After about four months, you will have nice vermicompost in the bin.  Add this to your garden!

A Double Decker bin

This bin will allow you to make compost in one bin, and then have the worms migrate on their own to a second bin.  This will save you the trouble of picking the worms out of your finished vermicompost.

Buy two dark plastic storage bins that are the same size.  Poke about 25 ¼ inch holes in the bottom of each bin.  These holes create a way for worms to travel from one bin to the other.

Set up your vermicomposting system in one of the bins (as described above for the single layer system).  When it’s time to use this compost, take the lid off of the bin, and stack the second bin inside the first bin.  The bottom of the second bin, with holes in it, should sit on top of the compost in the first bin.

Place bedding inside the second bin (as described above).  Add food scraps as described above.  Put a lid on this second bin.  The worms will migrate automatically from one bin to the one with the fresh bedding and food in it.  It will take a few weeks for them to make it to the fresh environment.  After they’ve migrated, you can take the compost from the first bin and enjoy using this treasure!

 A Ready-made Bin

Here is a pre-made bin that many people are very happy with.  This bin has three trays so there are more options for manipulating worms through the layers.  This “Worm Factory” also includes an instruction manual and DVD to help build confidence with this endeavor.    I like that his bin has many holes already drilled in the layers, making the drilling process unnecessary.

But the best part of the Worm Factory is that it also creates an easy way to extract the liquid fertilizer that is also generated through this process.  As waste is broken down, nutrient-rich liquid is generated.  This substance can be drained from the Worm Factory’s spigot and used as a liquid fertilizer for your plants.

Acquiring Worms

To gather worms from your garden, dig a hole about 2 feet square and then fill it with spent trimmings from the kitchen or garden.  Then cover with boards cardboard. After a couple of months the worms will have congregated in the hole.  You can then move them to your vermicompost bin, or move then around to various areas of your garden.

Click here for a source for the red worms that are recommended for vermicomposting.


Worms Eat My Garbage is a book that has more information on vermicomposting.