They are mentioned often in the Quran, the Bible and ancient Sumerian and Assyrian texts. Like all palm trees, date palms belong in the same botanical family as grasses, not fruits; that’s why, nutritionally speaking, they have more in common with grains than with most fruits. Dates contain potassium, protein, iron and other minerals; they can last for years and thus have been staples of the diet of nomadic people all over the Middle East for centuries.

Date palms from the Middle East began arriving in the United States about 100 years ago, when the Department of Agriculture began its effort to transform the arid regions of the Southwest into fruitful fields.

Image Mr. Wadi's wheat berries with roasted carrots, yogurt and medjool dates. Credit... Jenn Ackerman for The New York Times

Along with almonds, oranges, lemons and figs, dates are a drought-resistant crop that can flourish in desert conditions, and California’s Coachella Valley and the area around Yuma, Ariz., have proved ideal. (In that region, water for irrigation arrives via canals from the Colorado River, so the drought affecting Central and Northern California, which draw their water from the state’s northern mountain regions, is not as threatening.)

Robert Lower, the owner of Flying Disc Ranch in Thermal, Calif., has been growing dates and other fruits in the Coachella Valley since 1974. “I was looking for something no one else was growing,” Mr. Lower said. At the time, he said, the demand for dates had declined as other sources of sugar became plentiful. But over the years, with the growth of the Arab-American communities in Southern California and a rising awareness of the health benefits of dates, he now sells all the dates he can grow.

More and more of Mr. Lower’s customers at farmers’ markets, he said, are asking for barhi dates, one of the few types that can be eaten in its yellow unripe stage (called khalal in Arabic; fully ripe, tree-dried dates are tamar, meaning sweet). Mourad Lahlou, the chef at Mourad in San Francisco, grew up in Morocco and deploys khalal dates in the kitchen whenever he can get them. “When they are young, they are crunchy and only slightly sweet, with a hint of astringency,” he said, like a tart grape or crisp apple, making them great for balancing rich and savory dishes.

But the khalal date season is very short: They are available from California and Arizona only for a few weeks of the year.