Hardy Orange: A Velvety, Cold-Climate Citrus

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’ 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 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 species. And it has escaped: In the southeastern US, it is a significant invasive species. Further north, the cold seems to keep it in check.

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. But one commands a hefty price, while the other is hardly used, or is rumored to be inedible. The yuzu is respected, the hardy orange is undervalued and misunderstood.

Unlike most other citrus trees, the unusual and edible 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. And those leaves are distinctive, with three leaflets to each petiole. Another common name, trifoliate orange, describes that foliage, and echoes its current classification: 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 are two more hardy orange oddities. First, their downy skins seem to trap attract city pollution. You may find a darker film on the exposed side of the fruit. A good scrub washes this off effectively.  Second, 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.

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.

If you’re tempted to reach into the armed branches, you will emerge with puncture wounds. But take a careful hold of a branch, and shake: Thump-thump-thump. Then gather. Another advantage of gathering ripe, fallen fruit is that their flavor and juiciness seem to improve, with time. A hardy orange right off the tree will yield less juice than one that has been sitting on the counter for a week or more.

The sour fruits are important in Asian folk medicines and traditional Chinese medicine, where they are usually used dried and deployed as anti-inflammatories to treat digestive ulcers, gastritis, and dysentery. Science is substantiating these uses.

To make a fragrant hardy orange cheong (an uncooked Korean “marmalade”), layer equal volumes of washed, seeded slices with sugar in a jar. Leave at room temperature for about 5 days, shaking daily. Never leave the lid on tightly (fermentation may cause carbon dioxide to build up). On Day 6 transfer to the fridge.

The finished syrup can be used immediately, but I find it tastes better after a couple of months, and best after a year. Add a spoonful to boiling water for a soothing tea, shake it into a cocktail, or drizzle it into savory pan sauces.

Carrot Pickle with Hardy Orange

Hardy oranges are super-aromatic, but you could substitute yuzu or clementine zest if this pickle appeals. The recipe halves and doubles well.

• 1 lb carrots, peeled, sliced thinly into French-fry shapes
• ¼ cup avocado oil
• 3 Tablespoons mustard seed
• 1 teaspoon chile flakes
• 1 Tablespoon hardy orange juice (from about 6 fruit!)
• 2 teaspoons salt (this is 2% of the carrots’ weight)
• 2 teaspoons sugar
• ¼ teaspoon hardy orange zest, microplaned (from about 2 fruit)
• ¼ cup fresh lemon juice

In a small pot, warm the oil over medium heat and add the mustard and chile. Stir well for a minute, then turn off heat. In a bowl combine the carrots with the salt, sugar, the juices, the zest, and the warm mustard-oil mixture. Toss thoroughly. Transfer the carrots to a clean jar, cover loosely with a lid (to let gas escape if it starts to ferment), and leave on the counter for 4 days, shaking the jar daily to distribute juices. On Day 5 transfer to the refrigerator. Serve as a side, a topping for sandwiches, or add to salads.

See also:

• Yuzu Season Is Here: Rejoice, Harvest, and Make Yubeshi
• Winter Is Coming: How to Keep an Indoor Citrus Tree Happy
• Gardening 101: Persimmon Trees