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Composting class: Finding 'black gold' in Tam Valley

Olivia Kallai, 8, uses a magnifying glass to get a closer look at a worm during Worm Day on Saturday. Activities included instruction on worm composting, a worm beauty contest, worm races and worm coloring contest. (IJ photo/Jeff Vendsel)

It was Worm Day in Tamalpais Valley. 

On Saturday morning, Marin Master Gardener Joan Irwin led a class in worm composting at the Tam Valley Community Center.

"This is not rocket science," she told a group of a dozen or so people who gathered around a demonstration worm bin outside the center. "There's no scientific way of doing this."

Marin Master Gardener Joan Irwin lifts the lid on a compost bin to gather worms during the Worm Day program at the Tam Valley Community Center on Saturday. She said red wigglers, the same worms sold at bait shops for fishing, are the best for composting. (IJ photo/Jeff Vendsel)

There are, however, sound ecological reasons for composting kitchen waste and using worms to turn it into "black gold" to fertilize the garden.

"It keeps plastic bags filled with kitchen waste out of the landfills," Irwin pointed out. "It avoids the use of artificial chemical fertilizers. And your garden will love it."

In a compost bin of kitchen waste, worms will eat the organic material and leave behind their droppings, or castings, which are rich in nutrients for plants.

Irwin put it like this: "They eat, reproduce and poop. That's what you want."

Worm Day was not about any old worms. Red wigglers, the same worms sold at bait shops for fishing, are the best for composting, Irwin told the gathering.

They eat more and reproduce faster than your garden variety earth worm. Red wigglers consume half their own weight in food every day. In six months, eight of them can turn into 1,500.

Malcolm Harvey, a retired engineer, already knew that. He's been worm composting for a year now in what he calls "a worm condominium" he built himself. He likes red wigglers so much that he hates it when they inadvertently escape into his half-acre garden.

"It's difficult to part with my worms," he said with a straight face. "I love them so much."

The session was full of fun facts about worms. Who knew that worms have five pairs of hearts but no teeth or eyes? Even more fascinating, they're hermaphroditic, meaning each one is both male and female and mates with itself.

"An ideal society," commented Elizabeth Large, a naturopathic doctor from Mill Valley.

"I've already got a compost bin, but I didn't know if I was doing it right," she said, explaining why she came. "And I wasn't. I was putting way too many oranges in and not enough water. But it's amazing. With recycling and composting, I hardly have any trash."

She and the others were told that worms shouldn't be given citrus fruits or pineapple because those foods slow their reproductive system. You can counter that situation, however, with comfrey, an herb that increases a worm's sex drive.

Humans would do well to follow their diet. They eat most fruits and vegetables and avoid dairy products, meat or anything with fat. Like most of us, they love coffee and will chow down on coffee grounds, even eating the paper filters.

It sounds like an only-in-Marin joke, but red wigglers thrive on mango mulch. No need to go on a mango binge at Whole Foods. Mango mulch is available in bags from some nurseries.

Everyone who paid $5 Saturday got a one-person plastic worm bin - "a beginner kit," Irwin said - and a cup full of worms. Fliers were available that showed how to make worm bins from five-gallon plastic buckets. There was a model of a round, many-tiered commercial bin on display that's called "Can-O-Worms."

Worms are available free to Tam Valley residents from the community center bin.

Beginning composters on Saturday took home a handout touting worms as "one of nature's most important recyclers." It was titled "Composting with Worms: Raising Critters With a Sense of Humus."

Paul Liberatore can be reached at liberatore@marinij.com