Late fall brings the hardy orange, one of the most fragrant fruits of the season, to ripeness. When its small, velvety fruits drop to the ground from supremely thorny branches, the citrus connoisseurs pounce. The fruits’ velvety yellow rinds are thickly protective, so they land intact, sometimes lasting for weeks before deteriorating. Their intense aroma makes them a powerful base for hardy orange syrups and vinegars, and for a mouthwateringly tangy carrot pickle (whose recipe you will find below).
Photography by Marie Viljoen.
Hardy oranges can be compared with better-known yuzu. Both citrus fruits have big seeds relative to their size, and many of them. Both have very fragrant skins. Both have relatively little pulp and juice. One commands a hefty price. One is hardly used, or is rumored to be inedible.
Unlike other citrus trees, including yuzu, the unusual hardy orange is cold-tolerant. In theory, the tree can be grown down to USDA zone 5, whose minimum temperature is -20’F, although Michael Dirr, the acclaimed expert on woody plants, writes that at that temperature he has “seen it killed to the ground.” It will need shelter at that cold-extreme.
The tree is deciduous, losing its leaves in cold winters. Its leaves are distinctive, with three leaflets to each petiole. Another common name, trifoliate orange, describes that foliage. Botanically, the hardy orange’s current accepted classification is Citrus trifoliata. Poncirus trifoliata is a synonym, speaking to a debate as to whether it deserves its own genus, separate from Citrus.
For cooks and kitchen alchemists, there is another hardy orange oddity: a gummy residue coats knives and fingers, when you work with the fruit. The founders of Keepwell Vinegar, who use this citrus for an annual batch of their Bitter Lemon Vinegar, use rubbing alcohol or a baking soda paste to clean their knives and cutting board after processing. They ferment the fruit “for over a year,” they write in a message, “and by the time the ferment is over, the residue has lost its power.”
Bitter Lemon Vinegar from Keepwell Vinegar is $14 for 12.68 Fl oz.
Hardy oranges are native to East Asia (to China and Korea) and have been cultivated in Japan for centuries; they are also known as Chinese and Japanese bitter orange. The tree was brought to the United States early in the 19th century and was later used as rootstock for grafting with less hardy citrus. And it has escaped. In the southeastern US, trifoliate orange is a significant invasive species. Further north, the cold seems to keep it in check.
Perhaps the trifoliate orange should be called Thornus humungus. The trees’ long, green thorns are strong, sharp, and prolific. Need a security hedge or a living fence for wayward livestock? Look no further. “No sane person would attempt to penetrate this hedge!” writes Michael Dirr, in his nurseryperson’s bible, Manual of Woody Landscape Plants. The cultivar ‘Flying Dragon’ has corkscrew-twisted branches and thorns.
