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

Worms are not native to North America. About 20,000 years ago, our continent experienced an Ice Age, along with Europe and Asia. The phenomenon decimated the worm population, with the only survivors in parts of Turkey and the Mediterranean.

Over time, as Eurasians and Europeans began migrating to new lands, they brought plants for their new homes with them. Worms and other critters hitched a ride. On the East Coast of the U.S., these worms have changed the ecosystem because they eat the fallen leaves that trees also depend on for nutrition. This phenomenon is changing East Coast woodlands.

As the immigrant settlers moved across the country, so did their worms. In the Western U.S., worms have benefited the land and consequently the crops that people grow.

If you dig in damp soil, you will probably run across at least one worm. These earthworms (Lumbricus terrestris) live in the first 12 inches of soil. Their digestive systems turn soil into ever finer soil, and their castings improve the health of the soil. Worms also turn the soil, creating tunnels for water and roots. They won't thrive in compacted soil.

Night crawlers (Eisenia hortensis) also live in the soil. However, when the air is damp, they come to the surface and feed on plants there. They are much bigger than red wigglers. Once I put two night crawlers in a worm compost bin. When I cleaned the bin the following year, there were still just two night crawlers in the bottom of the bin. These worms had no interest in composting. However, some night crawlers from Europe and Africa will apparently do this work.

Red wigglers (Eisenia fetida, also known as fishing worms or manure worms), are the kings of composting. They are the worms you find under a stone, pot or pile of leaves. They only eat decaying matter.

Once I put a layer of maple leaves in one of my bins. I seem to have raked up some maple seeds, too, because a week later I had a crop of baby maples in my compost. The worms ate the leaves but not the seeds, which were still fresh enough to sprout.

Red wigglers eat or chew 90 percent of what you give them and that includes newsprint, plain cardboard, egg shells, daffodil leaves, spent flowers, vegetable leftovers, coffee grounds and animal fur. From these materials they produce compost, a mild fertilizer that you had a hand in.

Spread your worm compost over a garden bed, water it in, and the nutrients return to the soil. A lot of gardeners also put a little worm compost in the planting holes for their vegetables for an extra boost. I feed my potted plants with a handful of worm compost.

African red wigglers (Eudrilus eugeniae) grow much longer than our red wigglers and eat more. The two types can survive side by side because they are not necessarily interested in the same decaying material. The African worms need higher temperatures, but I have corresponded with someone in Michigan who is successful raising them in his garage.    

Other critters will move into your bins, too. Sow bugs or pill bugs will be the first to arrive, and their manure is just as good as worm castings. My compost-bin residents have included small toads, earwigs, slugs, snails, an occasional small snake (they like worms), a few lizards, ants and various flies. Most of these creatures coexist but I do get rid of the fruit flies.

This year I am experimenting with putting compost bins in my raised beds, a technique common to African keyhole gardens. I put a compost bin in the middle of each bed so the worms can travel back and forth and hopefully fertilize the bed they are in. Only time will tell whether this experiment is successful, but I will report back.

Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Rose Care” on Saturday, June 2, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Roses will grow without any care.  But they will thrive with a little TLC! Master Gardener rose experts will answer your questions regarding rose care at this popular forum. By June, the first spring blooms have faded, and many plants are beginning to show stress. Look for black spot, rust, mildew and aphids. Bring samples of what's plaguing your roses. Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment)

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.

Spring is here and it's time to clean and refresh your worm bed. You can harvest that precious gold—the worm castings—and use it to feed your plants.  

Years ago, I graduated to large compost bins for my worms. These bins need cleaning about every two years. If you are using a small container, you may need to clean it more often. I do add new bedding to the bins whenever the bedding gets about halfway down.  

If you have a small worm bin, you need to harvest the vermicompost, get the worms out and then return the worms to the bedding. There are several ways to do this.

In the past, when I had a small bin, I would remove the whole pile to a temporary container. I would put the worms and their castings on a screen with a mesh large enough that the worms could move through. I would place the screen over moist new bedding. Then I would expose the whole thing to a light bulb or to sunshine. Since worms are light sensitive, they would wriggle away from the light and into the fresh bedding.  

Another option is to use the plastic net sacks that onions and potatoes come in. Fill a sack with fresh, moistened bedding and put some of the worms' favorite foods inside. Then put the sack on top of the vermicompost and the worms will move into it, leaving the vermicompost behind for your use.

This method takes a little longer, but it's how I harvest my big bins. When the sack is full of worms, I dump it back onto the new bedding and the critters go back to work.

If you have big bins, you will have a bigger harvest and you need to prepare for it. Gather all the materials for the bedding: torn newsprint (no shiny coated paper), dried leaves, plain cardboard, straw, rice hulls, shredded paper. It feels good to put my old tax records in there.

When I have the bedding ready, I take the bin apart and set aside any uncomposted material. I put the composted material in a wheelbarrow so I can begin the process of separating worms and compost. I put the uncomposted matter back in the bin and then add the new materials. I don't try to mix them. Instead, I make a big “lasagna” of Iayered materials. As the worms eat their way through it, they do the mixing. Be sure to moisten all of the dry materials first, especially cardboard. When the bin is full, water it well. If the materials sink a bit, just add more.

I place a tarp over the castings in the wheelbarrow and put one or two of my sacks full of worms into the bedding. Every few days, I check the sacks and move the worms and contents to the new bin. Sometimes I add new worms at this point, purchased from a bait shop.

Once the worms have departed, I sift the compost to remove big items like sticks or peach pits. Then I put this sifted vermicompost into large pans in the sun to dry. When it's dry, I transfer it to a lidded storage container. (I use a garbage can.)

Scatter the castings around potted plants and in your beds, and your garden will thrive.

Workshop: U. C. Master Gardeners of Napa County will conduct a free workshop on “Worm Composting” on Saturday, March 19, from 9 a.m. to 11 a.m., at the University of California Cooperative Extension office, 1710 Soscol Avenue, Napa. Learn how to turn yard and kitchen scraps into rich compost to use as a soil amendment or garden mulch. Register here. No phone registration.

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.