Dekopon, also known as or shiranui, is a cross between a tangerine-like fruit known as kiyomi and a seedy orange from India known as ponkan. Bigger than most oranges but smaller than a grapefruit, the dekopon is immediately identifiable by a distinctive bulge at the stem end. Its name in fact is derived from the Japanese word for bump, “deko” and “pon” from the first syllable of ponkan. 

At first glance, the fruit might pass for a minneola or some other tangelo, the popular group of citrus fruits derived by crossing a tangerines with a grapefruits or pommelos. But none of those fruits has the distinctive aroma of this fruit, nor the profound sweetness of a dekopon.

Sweetness in fruit juices is measured in brix. Named for A. F. W. Brix, a nineteenth-century German inventor, who developed the scale, brix is most often associated with wine growing and wine-making. Each degree on the scale indicates 1 gram of sugar per 100 grams of juice. The average brix for oranges sold in the U.S. is just under 12 degrees. Using a high-tec gadget that measures brix with a light sensor placed on the surface of the fruit, Junichi Nishida carefully measures the brix of each fruit as its picked and he won’t sell his fruit unless it measures 14% or higher.

According to an article published in Japan Times in January of 2009, the fruit got its start in 1972 when scientist first crossed kiyomi and ponkan, but the fruits were considered less than promising because they didn’t hold well and the yields were low. But an unidentified grower from Kumamoto prefecture saw promise in the fruit and started growing it in earnest.

As Nishida lovingly snips a perfectly ripened specimen from one of his trees and subjects it to the brix test, it’s easy to imagine that he might have been that anonymous rogue grower who saw what others failed to see in the potential of this rising star in the citrus constellation. Nishida has an elfin quality as he moves gingerly over the slippery uneven, ground between the trees, which is covered in black plastic to retain moisture. Gesticulating and smiling as he moves, he animatedly explains how his fruits are coaxed to maturity.

“These trees are about thirty years old,” says Nishida through an interpreter. “They reach their peak production at about twenty years of age. A single tree at peak production yields about 320 pounds of fruit.”

All Nishida’s fruit is certified organic and the certification standards prohibit the use of any fertilizers. “You see how these leaves are yellow,” he says, pointing out a few leaves that are paler than the vibrant green ones around them. “This is an indication that the tree needs nutrients; if I were a conventional grower, I would fertilize the trees. But I have discovered that a tree that’s struggling produces sweeter fruits.”

“I keep watering to minimum too so that the juices will be more concentrated.” From June to November the greenhouses are uncovered so that the trees are exposed to rainfall. If it’s a very dry year, he will give the trees water. “Usually I don’t have to.” During harvest season, the trees are covered, and in very cold weather, a heater is turned on the greenhouses. “The cover helps the orchard retain some heat, but it’s primary function is to protect the fruit from birds.”

“We select the largest fruits for the gift boxes,” says Nishida, each one weighs in at about 12 ounces. “But people are asking for smaller variety for home.”

The largest fruits are cradled in padded boxes, ten fruits per box and sold on-line for about 5,000 yen (roughly 50 dollars, U.S. per box). Through an informal U-pick arrangement, neighbors are invited to pick their own fruits at a reduced price. Harvest is in March and shipping continues through April. Other citrus fruits from his greenhouses are harvested from December through February. The Nishidas employ four full time workers and two local women work part time during harvest season, pruning the trees as they harvest.

“I wanted to grow citrus to supplement the peaches and other summer fruits,” says Nishida. Peaches ripen in summer and citrus fruits ripen in the winter. Now in addition to his peach orchards he has six greenhouses, three of them filled with dekopon; he also grows lemons, satsuma mandarins and a small number of yuzu, the vibrant fruit that gives ponzu sauce its punch. “This year, I’m adding a few blood oranges.”

Some of the fruit is converted into bottled juices, also sold on line. Unshu simikon, the familiar satsuma mandarin is the variety from which Nishida makes most of his bottled juice. The Satsuma juice sells for about fifteen dollars for a one-liter bottle, while the pure dekopon juice costs fifteen dollars for a bottle half that size, marketed in elegant paper-wrapped bottles and the juice is pasteurized and sealed to remain shelf stable for at least ninety days. Both juices are made from the whole fruit, not just the pulp and they pack a powerful punch. The bar at the Four Seasons Hotel in Tokyo uses the Nishidas’ juice exclusively for their signature mimosas, cutting the sumptuous juice with a splash of champagne to make their signature brunch cocktail.

In addition to the juices, Nishida contracts a local company to produce sorbets and ice creams with his fruit. The peach ice cream is swirled with peach sorbet and the dokopon sorbet is startlingly vibrant. A chocolate ice cream infused with essence of dekopon is almost unbelievably flavorful.

Inside the greenhouse, Nishida distributes samples of the frozen confections to reporters, his wife Noboku spoons samples of lemon curd and orange marmalade onto small squares of white bread. The preserves are vibrantly colored and brilliantly flavored. But none of the value added products the Nishidas produce can outshine the brilliant dekopon in its purest form. Considering the rarity and quality of this fruit, ten oranges for fifty dollars seems like and incredible bargain.