Fresh sour cherries are a visual feast. If you're lucky enough to find them at the market, you'll see vibrant fire-engine red fruits, with yellow interior flesh. Sour cherries are smaller than their sweet cousins, with a moderately acidic flavor and firmer texture. Too tart to be eaten out of hand, they're traditionally used in pies, tarts, cakes, cordials, confections, and jams, as well as slighly sweetened sauces for poultry. Look for them in late June and July, a few weeks after sweet cherries have reached the market. Montmorency is the most common variety.
The United States is one of the world's largest sour cherry producers, and almost the entire crop, grown mainly in Michigan, is used for processed cherry products, including canned cherries, pie filling, frozen loose cherries, dried cherries, cherry juice, and cherry brandy.
At the market, choose sour cherries that are soft and juicy, like ripe plums. Their thin skins are extremely fragile, so you may see a few bruises. Handle the fruits as you would delicate raspberries and refrigerate them as soon as you get them home.
Sour cherries taste best when cooked. The heat turns their plump and tender skins creamy and develops their flavor—intense and fresh, with just a little acidity.
Treat all cherries with the same light touch you give to berries. Keep them refrigerated for up to five days uncovered, rather than in a sealed plastic bag.
If you're lucky enough to have more sour cherries than you can use in a few days' time, freeze the extra; it's the best way to hold them. Pit the cherries first, then freeze them in a single layer on parchment-lined baking sheets for three or four hours, and then seal the frozen cherries in doubled zip-top bags. They'll keep for up to a year in the freezer.