One of three ancestral species of cultivated citrus fruit, the citron looks like a large, lumpy lemon with a thick rind. You're unlikely to see it in stores or farmers markets but this time of year, you might see it used during Sukkot, the Jewish harvest festival. As a journalist, David Karp became so fascinated with citron, called etrog in Hebrew, that he made a career change and has spent the last 25 years in academia, studying fruit. Unlike lemons, the citron doesn't produce much juice. Instead, it's prized for its thick rind, which is candied and diced, and often found in fruitcake and panettone. Karp contributed four essays to The Citron Compendium.
We've also talked to Karp many times in the past… about sour cherries, Gravenstein apples, Dekopon mandarins, Crane melons and why the future of California lemons is seedless.