Sour Cherries
Most tart cherries in the United States are grown in Michigan. There are fewer than 10 acres growing in California, primarly due to the climate.
Compared with sweet cherries, sour cherries are smaller and softer, with acidity, flavor of the stone and a slight bitterness that shine through when cooked. They are indispensable for making pie, preserves, soup, brandy and albaloo polo, a Persian rice dish. Recently, tart cherry juice and dried fruit have become popular, as medical studies have shown that the fruit may have anti-inflammatory and disease-fighting properties.
Also known as tart or pie cherries, this fruit is available canned or frozen, but there are many bakers, jam makers and home cooks who seriously prefer the fresh fruit.
Cultivation
Compared with sweet cherry trees, sour cherry trees are much more cold hardy, and so they are more commonly grown in areas with frigid winters, such as Russia, Eastern Europe and the U.S. Midwest.
A century ago, Midwestern farmers grew dozens of varieties of sour cherries, but today, 99% of the domestic crop is of one centuries-old French type called Montmorency, and almost all of the harvest is processed. Because sour cherries are so delicate and because of quarantine restrictions for pests, fresh sour cherries from the Midwest rarely reach California markets.
Sour cherries are actually from a different species than sweet cherries such as Bing. They're a natural hybrid of sweet cherry with ground cherry, a cold-hardy bush that bears tiny, very tart and astringent fruit.
Harvest
Harvest of sour cherries is painstaking. The fruit has to be hand-picked so they keep their stems and don't leak or spoil. The fruit is soft and must be handled gently.