Ranging from two to four feet high, the ragged plants offer up thousands of tiny, off-white puffs of rapidly fading blossoms. They look more like weeds than like the average person's concept of lettuce--but that's what they are, a mixture of different varieties of lettuce plants. They've been deliberately allowed to go to seed, which next year will be used to grow a salad mix for Julia's Kitchen, the acclaimed restaurant at COPIA, Napa's food and wine center.

From a small mound of dirt, corn stalks soar skyward. A flowering bean vine with bright red-orange blossoms winds its way upward around the stalks. The wide green leaves of a squash plant hug the ground. The corn serves as a trellis for the bean vine, letting it flourish. The bean plant adds nitrogen to the soil, giving added nutrients to the corn. And the squash is a living mulch, protecting the roots of all three from the moisture-robbing sun. This is a traditional and popular Native American gardening technique called the Three Sisters, and it's one of the many living displays in COPIA's Edible Garden, says head gardener Geoff Palla. The neat square illustrating the Three Sisters growing pattern contains several mounds, each one planted with different varieties of corn, beans and squash.

"If you have just one variety and it fails, then all your food has failed," Palla explains. "Whereas if you planted five different varieties and two fail and three make it, you still have food. Every variety has its little nuances of what it can resist as far as disease and what kind of weather and soils it can withstand. Diversity is really much stronger in the end."

In the pursuit of diversity, COPIA not only gathers its own seeds, it buys from a range of suppliers, such as Seeds of Change, Native Seed Search and conventional seed catalogues. It is also a member of the Seed Savers Exchange, a national network of gardeners who swap seeds with each other at a minimal cost.

"This is a large group of people who are really preserving diversity. Actively preserving it," Palla enthuses. "Growing the seed, saving it, telling everyone else they have it and sharing it."

These scraggly-looking plants are an integral part of COPIA's multipronged approach to gardening. Its 3.5-acre Edible Garden is informative and educational, illustrating both long-term traditions and new trends. The site is also productive, supplying 60 percent to 70 percent of the fruits and vegetables used in COPIA's kitchens. And the Edible Garden is focused on stewardship--drawing seeds and plants from a variety of sources, saving a diverse range of seeds and nurturing not just the plants but soil health as well.

One sister: Beans and squash and corn grown together support each other.

It's an overall view rather than the neatly organized but fundamentally limited corporate approach to gardening, and COPIA is one of the many sites nationwide where nature's untidy diversity is being nurtured rather than discouraged.

All this will be celebrated Aug. 11-12 at COPIA's fourth annual Edible Gardens Festival. The event is appropriately diverse, featuring cooking demonstrations, food, wine, live music, art, kids' craft activities, presentations by gardening experts and, of course, the chance to relax, enjoy and learn in COPIA's Edible Garden. The seedy lettuce plants are just a part of the whole.

"A neat and tidy garden may look good, but it isn't what nature intended and you will have a hard time keeping it up," explains Marc Cool, seed director for Seeds of Change, one of the sponsors of this weekend's festival. Growing more than 1,000 varieties of plants and selling over 600 different organically-grown seeds, the New Mexico-based Seeds of Change is aimed at preserving biodiversity and promoting sustainable, organic agriculture. Cool will be at COPIA this weekend, talking about biodiversity in the garden. Just as people benefit from and adapt to diverse experiences in life, so too do plants.

"The interrelationships between all the different plants are really interesting to me," Cool explains. "It's a lot like people living together. Plants do interact and they adapt genetically to those interactions."

Diversity, Cool asserts, is what nature intended. "A vegetable will grow better if there's a certain flower nearby, because it attracts pollinators. Mixing up different species is important."

"You shouldn't be afraid to let your garden teach you what it does best," Cool adds. "When you have a garden and things grow, what does best is what works there."

In a back corner of the garden, some tomato plants are struggling. They're struggling on purpose, because Palla and the other four members of the garden staff aren't giving them much water. "We're stressing the heck out of them, giving them very little water, and what we're getting is a much smaller yield, much smaller fruit but the flavor is so intensified," he explains.

These particular tomato plants are the popular Early Girl variety, which is grown commercially in California's Central Valley. A lot more fruit is produced by the well-irrigated plants in these commercial fields, but it's nowhere near as flavorful as what's being grown on those dry-farmed at COPIA.

The average home gardener doesn't necessarily need a high yield, so it could be worthwhile to set aside one tomato plant, carefully underwater it and see what happens. Or let the lettuce or some other crop go to seed, and use those same seeds next year.

"I like to let things take their whole life cycle all the way to seed and then back down," Palla says. "Then what you get is a lot of volunteer stuff, and you can literally manage patches of things. It's a great concept for home gardeners."

This might not create a picture-perfect garden, but it will make it a healthy one.

"A lot of things that we think look neat and tidy and perfect--well, the plant doesn't know anything about what we think is neat and tidy and perfect, nor does it benefit from a lot of that stuff."

One of the things Palla enjoys about gardening is that there is no one golden rule that all must follow. "Everyone comes up with their own little nuance or truth that they think works for them, and it does for them. That's what I love about it."

"It's kind of like baking," he adds enthusiastically. "Everyone does it a little bit differently, and yet it still comes out great."

Edible Garden Festival runs Saturday-Sunday, Aug. 11-12, at COPIA. 500 First St., Napa. 11am to 6pm. $10-$15 (children free); wine tasting $10. 1.888.512.6742.

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