Clean up Your Worm Beds

Oct 4, 2019

by Penny Pawl, U.C. Master Gardener of Napa County

Over the years, many people have attended compost workshops conducted by the City and County of Napa and the Napa County Master Gardeners. I have been teaching the worm compost classes and always wonder if the people who made worm bins got all the information they needed to clean the bed when the time comes.

Worms are important composters as they eat 90 percent of what is given them. Their castings(aka worm poop) provide a balanced fertilizer for plants. Over time, they will eat newsprint, dried leaves, straw, coffee grounds, eggshells and various fruits and vegetables.

Sometime after you create your worm bin and worms have been chomping on your kitchen scraps, you will need to separate the castings from the other things you have been feeding them. When you do this, you will see that the worms have transformed most of the newsprint and other bedding into a fine soil-like product.

If you are still using the 18-gallon tub you received at the workshop, you can move the finished compost to one side of the container and build new bedding on the other side. Feed the worms only on the new side and, over time, the worms will move into the new bedding. Then you can remove the old bedding to dry and remove any unfinished compost.

Another approach is to remove all the old bedding and build a new bin. However, you want your working worms to move into the new bedding. The easiest way to achieve this is to put the old bedding on a screen on top of the new and expose it to light. Worms are light sensitive. To escape the light, they will move down into the new bedding. I tried this in one large worm bin years ago and the worms had relocated in a half hour.

I compost in much larger containers. My method for harvesting the castings is to remove all the finished bedding to a wheelbarrow and rebuild the bedding with new materials. I use the “lasagna” method of layering materials. Remember to dampen all the materials as you layer them. They should be as moist as a wrung-out sponge. Worms breathe through their whole bodies and need to be kept moist.

To coax my worms out of the old bedding so I can put them back to work, I use the mesh bags that potatoes and apples are sold in. I fill those bags with new bedding and favorite foods of the worms and bury the bags in the old compost. In a few days, the worms will move from the old compost into the bags, and I can then transfer the content of the bags to in the new bedding. Another method is to place a large screen with old compost on it over the new bin and let the worms sort themselves.

Once the worms have moved out of the old compost, I dry the compost in the sun and then sift it. Any large pieces go back into the bin. If the compost is clumpy, I put it on a tarp or and walk on it to break it up before sifting.
Make sure the compost is dry before storing it. Otherwise, it may mold.

You can spread the compost directly on garden beds. I usually sprinkle it around the plants and water it in. I also put a little scoop in planting holes to give the roots of new plants a boost.

Fall Faire: U.C. Master Gardeners of Napa County's second annual Fall Faire will take place on Saturday, October 5, from noon to 4 p.m., at 1710 Soscol Avenue in Napa. Tickets are $5 for adults. Children 15 and under are free with an accompanying adult. Purchase tickets online with a credit card. Cash and check only will be accepted at the door. Find more on the Fall Faire at

Next workshop: U.C. Master Gardeners of Napa County will hold a workshop on “Stinking Roses and Edible Alliums: Grow These Essentials for Your Kitchen” on Saturday, October 12, from 9:30 to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. For more details & online Registration go to or call 707-253-4221.

The UC Master Gardeners of Napa County are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website ( or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.