With their rainbow colors and odd shapes and sizes, the appeal of heirloom tomatoes is undeniable. But more than just a pretty face, these darlings of the summer farmers market also represent diversity and freedom in our food supply.

“People ask me, ‘Is this heirloom or hybrid?’” says farmer Bill Crepps of the Winters, California farm Everything Under the Sun. “You can tell that there’s something they don’t like about the word ‘hybrid.’”

Crepps, who grows more than 20 varieties of tomatoes, recognizes the allure of heirlooms. But he also thinks hybrids have received a bad rap, in part because people confuse them with genetically engineered (or GMO) plants. He believes that hybrids hold an important place on small, diverse farms. “I grow heirlooms for their variety, but I rely on hybrids for their disease resistance,” he says.

Seeds with Heritage

Most people associate “heirloom” with big, juicy slicing tomatoes like Brandywine, Black Krim, and Marvel Stripe, but they come in all shapes and sizes, including the San Marzano paste tomato.

Heirlooms are varieties whose seeds have been saved by farmers and gardeners and passed down for generations, usually 50 years or more. They are also open-pollinated, which means that they can be pollinated through natural mechanisms (such as insects, birds, and wind) and still breed true-to-type. Their seeds can be saved and replanted with fairly consistent results, and they tend to be genetically diverse, making them more adaptable to different growing conditions. Unlike hybrids and GMOs,  open-pollinated varieties cannot be patented.

In the 1980s, Ben Lucero of Lucero Organic Farms in Lodi, California set out to develop his own tomato after discovering that one of his plants’ seeds yielded an array of unusual offspring. After about five years of isolating the good plants, saving their seed, and replanting, he created  the Ivory Pear, a pale yellow, pear-shaped cherry tomato bursting with flavor. Though still too young to technically be an heirloom, the Ivory Pear is sold in seed catalogs that specialize in them.

These days, Lucero gets most of his seed from such catalogs. “I save some seeds that are harder to get, and I would save more, but I don’t really have the time,” he says.

Hybrid Hype

In contrast to open-pollinated seed, hybrid seed is created by cross-pollinating two different varieties to yield offspring with desirable traits from both parent plants, such as disease resistance, uniformity, and high yield—a phenomenon known as “hybrid vigor.” Early Girl, Sun Gold, and Juliet are just a few of the popular hybrid tomatoes found at farmers markets.

But hybrids should not be confused with GMOs. While hybrids are crossed manually in the field, GMOs are created using high-tech methods such as gene splicing, sometimes combining genes from different species to yield organisms that could not occur in nature.

While some argue that hybrids are more reliable and hardy than heirlooms, they also have serious drawbacks. Seeds from a first-generation hybrid (called “F1”) are not genetically stable, which means that farmers cannot save and plant them with reliable results, so they must buy new seeds every year. Seed companies that hold the patents can control their production—a big sticking point for farmers and eaters concerned about corporate consolidation in the food system.

Early Girl ≠ GMO

Farmer Joe Schirmer at Dirty Girl Produce has been growing hybrid Early Girl tomatoes in Santa Cruz, California since 2000. With its thick skin, compact round shape, and deeply concentrated flavor, the dry-farmed Early Girl has earned a cult following in the Bay Area. But Joe has also noticed backlash against the tomato in recent years.

“People are saying, ‘Early Girl is made by Monsanto,’” says Schirmer. “It’s not.”

The variety was originally developed in France and distributed by a company called Petoseed, which was later acquired by Seminis. In 2005, Seminis was acquired by Monsanto, a company well known for its GMO seeds, muddying the Early Girl’s pedigree. (The patent has expired, but the Seminis still controls the parent stock.)

Schirmer sees the GMO debate as obscuring deeper problems, such as corporate control and overuse of pesticides in industrial agriculture. “If everyone wants to boycott Monsanto, they’re going to have a hard time. They own lots of seed companies as investments,” he says. “They’re patent trolls. They want to own anything they can, so that farmers rely on them to buy it every year.”

A New Girl on the Block

About six years ago, Schirmer started saving seed from his Early Girls. “It was more out of curiosity than anything else,” he says. “And of course there’s also the idea of seed security, and not having to rely on seed growers.”

Plus, Schirmer wanted to see if he could breed a tomato that would be better suited to his coastal climate and resistant to Phytophthora, a type of mold that can wipe out a whole crop. After one of his plots was hit with the disease, he cleared the field but some of the plants had seeded, leaving a new generation to grow. “I saw every kind of tomato imaginable—big ones, little ones, spindly plants—but there were a few in the mix that were just perfect.”

Schirmer cleared out the oddballs and left the good ones to grow, then saved their seeds. When he replanted the next year, there was a higher percentage of good tomatoes, and even more the following year. Several generations later, he had created his own open-pollinated Early Girl spinoff, which he dubbed the Dirty Girl.

Hybrid to Heirloom?

This year Schirmer planted 3,000 Dirty Girl plants, in addition to 70,000 dry-farmed Early Girl plants, and he started bringing a small crop of Dirty Girls to the farmers market for a trial run.

While the Dirty Girl is becoming more vigorous and uniform, and the flavor and texture are on par with its hybrid ancestor, Schirmer says they won’t replace the Early Girls on his farm any time soon.  “If over the next 10 years, I could get it to a place where I felt like it was out-producing in yield, flavor, and quality and wasn’t prone to Phytophthora, then great. But I’m nowhere near that,” he says.

Like Lucero’s Ivory Pear, the Dirty Girl may be on its way to heirloom status, but until then, Schirmer will continue to buy the commercial hybrid seeds.

“I have no problem with Early Girl,” he says. “But I wish that some other seed company that I could stand behind would produce them.”

A version of this story appeared on the Center for Urban Education about Sustainable Agriculture (CUESA)‘s website.