Worms can be your best friends, at least when it comes to eating kitchen waste and producing some of the best organic fertilizer you can get your grubby gardener's hands on.

Starting and maintaining a worm bin is easy, says Contra Costa Master Gardener Kathy Southern, speaker at this week's Our Garden class. Here are her tips.

The dirt on worms

  • Worms are used in industrial settings to aerate, sanitize and deodorize some types of contaminated waste sludge.

  • Worms have no eyes, ears, teeth or lungs. They still manage to find their way to food and by eating a little grit with their food and using the muscles in their bodies, they are able to swallow and digest soft foods.

    "Red wigglers" are among the best for worm composting bins.Joan Morris/Staff
    "Red wigglers" are among the best for worm composting bins. Joan Morris/Staff ( Joan Morris )

  • A worm breathes through its skin, extracting oxygen from air and water that passes over its skin and blood capillaries. If the worm dries up, it dies from suffocation.

    What type to get?

  • Red wigglers (Eisenia foetida)

  • Red worms (Lumbricus rebellus)

  • Worms that you find crawling around your garden are not suitable for worm bins. The earthworms live in a different environment from the red worms and thus won't live long in a bin.

    Getting set

  • Worms need adequate temperatures, moisture and ventilation. They can die if the get too hot or too cold.

  • Buy a worm bin or make your own by drilling holes in a 10- to12-gallon storage bin.

  • Soak shredded newspaper or cardboard in water, then wring out most of the water so that the paper is damp but not soggy. Add it to the bin. This will serve as bedding material as well as food.

  • Add your worms and then cover them with another layer of shredded, damp material.

  • Cover the bin and place it in a protected area, out of the sun. In the winter, the bin will need a warm place.

  • Allow the worms to get accustomed to the bin for two or three days, then add food.

    What to feed them

  • Fruits and vegetable scraps

  • Manure (vegetarian, such as from horses or cows)

  • Coffee grounds

  • Tea bags

  • Finely crushed egg shells

  • Paper

    Don't feed them

  • Dairy products

  • Fats and oils

  • Meat or fish

  • Feces

  • Citrus

  • Twigs and branches

    The reward

  • Worms produce, to put it politely, worm manure. The castings are full of beneficial microbes and nutrients, and adding them to your soil also can improve the tilth.

  • Worm castings contain five times more nitrogen, seven times more phosphorus, 1½ times more calcium and 11 times more potassium than regular soil.

  • Harvest the castings by separating the worms from the black, rich material they are living in. These are the castings.

  • Watch for small yellow balls -- these are worm eggs and shouldn't be wasted. Return the worms and the eggs back to the bin along with fresh bedding and food.

    Final thoughts

  • Worms don't require constant attention. If you provide them with enough food, you can even go on vacation for two weeks and they will be.

  • When first starting your bin, pay attention to how much food is being consumed and the number of worms you have. Feed accordingly.

  • Commercial bins typically have several trays plus a container or spigot to drain excess moisture from the bin. When first starting, just use one tray. As your worm population increases, divide them and start another tray. The worms will travel up to the next level in search of food, leaving behind a tray full of compost for you to harvest.

    About Our Garden

    Free gardening classes are offered 10-11 a.m. on Wednesdays at the garden, Wiget Lane and Shadelands Drive in Walnut Creek. Master Gardeners also are available to answer questions at the Help Desk; plants, seeds and worm compost also are available for sale most weeks.

    Next time: "Winter Care of Fruit Trees" with Terry Lippert.

    -- Joan Morris, Staff