Over the Garden Gate: The dirt on raising earthworms for vermicompost

We all know earthworms can be beneficial in our gardens, but did you know that you can incorporate them into your compost sites or start a composting bin centered on using earthworms to your benefit?

There are more than 9,000 species of earthworms, but the common red wiggler (Eisenia fetida) is the one recommended for compost bins. These earthworms will help to break down organic matter put in compost piles and reward you with vermicompost, which you can add to gardens.

Here we focus on developing a suitable earthworm bed in order to utilize vermicompost produced.

Raising earthworms to aid in recycling food waste requires minimum space or maintenance. Worms will produce vermicompost, a high-quality additive for your garden. A side benefit is that you will have free earthworms for fishing.

Vermicompost is produced from waste of earthworms and is a blend of castings and decomposed organic matter that has been placed in a worm bin.

Nutrient content of vermicompost will greatly depend on what you feed worms and type of bedding you provide. Vermicompost can aid in plant growth, constrain diseases and increase microbial activity in soil. It contains nitrogen, phosphorus, potassium, calcium and magnesium in a form that is easily used by plants. Applying vermicompost also improves water retention, aeration and absorbency in soil.

To create a vermicompost bin, you will need a container for the worm bed, bedding, red wigglers (recommended species) and food scraps.

An outdoor container may be constructed from any number of materials, including concrete blocks, lumber, brick or plastic bins. If using lumber, do not use aromatic lumber, such as cedar, because it contains tannic acid that can be harmful to worms. Never use treated lumber. During winter, soil or straw can be piled against edges of the bin and on top to protect worms from cold weather. Do not add food to outdoor bins in winter.

For an indoor container, you may find that a plastic bin works best. Size will depend on your needs and portability. It can be as small as a shoe box or much larger. You will want to choose a dark or solid color with a lid (to keep light out and worms in) as worms do not like light. You will also need to drill many tiny air holes in the plastic as worms need oxygen and drainage. Placing a plastic bin inside another solid one assures that no leakage will end up on your floor or lost to use as fertilizer. Moisture that forms and drains out is liquid fertilizer that you can use in home landscape.

When properly maintained, the worm bed has no odor.

Bins should be 12 to 24 inches deep. Bedding materials should take up about half the depth and can include compost, shredded paper, brown leaves or aged manure. Mix in some garden soil to aid worms in their digestive process.

Worms will eat the bedding in addition to food scraps you provide, so you will need to continue to add bedding to their home. Bedding needs to be kept moist similar to a wrung-out sponge. Never pour water into your worm bin, you should spritz with water to maintain about an 80 percent water ratio after establishing the bed.

The bed and surrounding area should be between 59 and 77 degrees. You can hang a small thermometer from the side of the bin to check temperature. The container should never be set where sunlight or very warm temperatures will heat it up excessively.

Red wigglers (Eisenia fetida) are the recommended species for earthworm farming. Do not obtain your worms from a bait shop or your yard as you will not know the species. For example, there are Asian invasive species known as jumping earthworms (Amynthas spp.) that strip the soil of its humus layer and thus impact native fauna and flora.

It is important to only buy worms from a reputable dealer for this purpose. You need to start with a minimum of one pound of earthworms (approximately 1,000) per square foot of bedding. One pound of earthworms will eat about two pounds of food scraps per week.

Some things red wigglers can be fed are vegetables, fruits, eggshells, coffee grounds and shredded coffee filters. They prefer watermelon rinds, pumpkin and cantaloupe. Just assure that food scraps, grounds, tea bags or eggshells are shredded or cut into small pieces. Avoid citrus, starchy foods and protein (bones, dairy, and meats). You can also freeze scraps to be added later.

You should cover whatever scraps you add to the bed with some of the existing bedding. You can use a small garden tool to do this being careful not to disturb the worms in the process. This will discourage flies and other pests from invading the worm farm prior to the worms decomposing what you add. Fine screening or moist newspaper can also be used as a covering.

About 4 months later, you can start harvesting vermicompost to use on garden plants. Common harvest methods include sieving or screening to separate worms and large pieces of food and bedding from small worm castings, which are vermicompost. Baiting is an easy practice where you put all food for a few weeks into one side of the bin to lure worms away from the side where you want to remove compost. The opposite practice will draw worms to a location where it will be much easier to harvest vermicompost. Incorporate into soil and protect from direct sunlight to enhance its use.

This method of raising earthworms for recycling and recreation can be done anywhere -- on a balcony, in a garage, or even in a closet. Earthworm farming is very beneficial to your garden and not labor intensive after the initial preparation of the bin.

Dawn McCune is a Master Gardener intern with Penn State Extension -- Beaver County.