How the pomelo, grapefruit, Oroblanco, cocktail, lemon, Meyer lemon, citron, Kaffir lime, mandarin, blood orange and tangelo originated in the shadow of the Himalayas, traveled their separate ways, and got back together again in California's farmers markets

Eons ago, the citrus family of fruit diverged in three general directions from a point of origin in the shadow of the Himalayan mountains near present-day Bhutan. A wide array of representatives from each major branch of the family—and many in between—reunite each winter in farmers markets across southern California.

The line of citrus that branched into southeast Asia yielded the pomelo (also spelled pummelo). In another time and place, the pomelo would sire the grapefruit, which now far overshadows its southeast Asian granddad in the United States. But dozens of southern California market farmers are bringing the pomelo back.

Pomelos certainly contribute visual drama to the winter markets. They look like overinflated grapefruits. The largest are the size of bowling balls. They have a thick peel and even thicker layer of white pith, which accounts for the pomelo’s appeal to preservers. The flesh is sweeter and chewier than grapefruit.

Most of the customers for pomelos fall into one of two categories, says Fred Campbell, a Fallbrook grower. There are those who have never seen a pomelo before and exclaim, "What the heck is that!" And there are Asian customers who know it well, and are often so particular about it that they want it with a stem and leaf attached.

What do you do with a pomelo leaf? The Food of China, by E.N. Anderson, has this suggestion: "Water in which pomelo skins or leaves have been soaked is commonly used to drive away ghosts and evil spirits."

The grapefruit is recognized as a distinct species of citrus. But it was never mentioned in ancient Chinese texts that catalogued other citrus fruits, leading botanists to suspect that it got its start outside of Asia from a cross in the wild between a pomelo and a sweet orange. Some have gone so far as to peg the union to the Caribbean in the 1750s. (About a century earlier an English seafarer, Captain Shaddock, brought the pomelo to the West Indies, where it joined the orange, which was introduced by Columbus on his second voyage in 1494.)

Grapefruit need long periods of uninterrupted heat to get sweet and stay thin-skinned. So farmers in coastal counties couldn’t grow them—until plant breeders at the University of California’s Citrus Research Center in Riverside came to the rescue with genes from a pomelo. Out of their efforts to breed a cooler-climate grapefruit, the Oroblanco and Mellowgold were born in 1958. They are siblings from a cross made that year between a Siamese acidless pomelo from Thailand and a white grapefruit, says Dr. Mikeal Roose, a botanist at the university.

They have the eye-catching heft of their Thai parent but have a thinner skin. They are sweeter than straight grapefruit, even when grown in a cool climate. Moreover, since the pomelo has two sets of chromosomes while the grapefruit has four, the offspring were left with three, which renders them seedless.

Researchers at the university crossed the same Thai pomelo with a mandarin to produce another interesting hybrid, a sweet, easy-to-peel (but seedy) fruit called the cocktail, which occasionally turns up in farmers markets. Unlike the Mellowgold and Oroblanco, which were patented in 1981, the cocktail was never officially released by the university. Apparently someone swiped a bud years ago, says Roose. All the cocktails out there today are clones of it.

Lemons are the leading scion of the line of citrus that branched south from the Himalayan foothills into the plains of today’s India and Pakistan. One of the oldest artistic representations of a citrus fruit, an earring found at 4,000-year-old Mohenjo-Daro in the Indus River valley, depicts a lemon. Or perhaps it is a citron, an older species that may have spun off lemons somewhere along the evolutionary trail.

A handful of certified producers in southern California grow citrons, including Steven White, of Escondido, who has 30 trees. They are grown for their peel and pith, which is fortunate: there’s not much else to a citron. Candied, the peel shows up most often in fruitcake. White says citrons are also used in both Jewish and Chinese religious ceremonies.

Other people use citrons as an air freshener. When the skin is scored, they exude a refreshing citrus aroma for several weeks, after which they can still be chopped up and sprinkled over vegetables or fish, White says.

White grows another old oddball, the Kaffir lime. White says Kaffirs are grown primarily for their leaves, which are used in Thai cooking. But when he took some of the fruit to the Carlsbad market not long ago, pretty much on a lark, he was surprised to find that Vietnamese women snapped them up. White has learned that they juice the Kaffir limes, which are extremely acidic, and use it for a hair wash.

At the opposite end of the sweet-sour spectrum, the Meyer lemon is one of the more modern additions to the family. It is a relatively sweet fruit that botanist presume to be the product of a cross between a lemon and an orange that occurred in China sometime in the last 300 or 400 years.

A third citrus line to diverge from the family’s point of origin in south Asia, the oranges and mandarins, branched to the north into China. Not long ago, mandarins, also known as tangerines, were a treat that arrived around Christmas. Now, one variety is widely available as early as late October. By March many who grow for farmers markets are more than half way through the succession of six or more different varieties that they grow to assure a staggered harvest. Fremonts and Pixies are among the most common midseason varieties.

Plain old oranges, which tend to be mid-season valencias this time of year, are not without their own genetic variations. The blood orange, for example, is a member of the citrus family that may have evolved in Malta or Sicily within the last several centuries.

Campbell, of Fallbrook, has more than 500 trees of the variety, which he says was common in California in the 1930s when he was growing up. He prefers to call them Moro Burgundy oranges instead of blood oranges. "That name doesn’t sit too well with the ladies," he explains.

The tangelo is another wayward cousin in the citrus clan, a cross between a white marsh grapefruit and a Dancy tangerine. A seedless fruit that is easy to peel, tangelos are harvested from late January to June. The tangelo embodies the genetic range of the citrus clan, all in one fruit. "It begins the season tasting like a grapefruit. It ends the season like a sweet tangerine," explains Jeanne Warren, of the Tangelo Rancho, in Piru.

Tangelos are also fickle about their shape. They "want to be a different shape every year," says Warren. They’re usually pear-shaped, but rarely round, so they can’t be readily handled by the packing houses and therefore don’t often turn up in supermarkets.