Black plums, also called Italian prune plums or just prune plums, are a small, oval, clingstone variety of plum with deep purple-black skin and yellow-green flesh, believed to have originated near the Caucasus/Black Sea region. They're sweeter and less watery than most eating plums, with a firm texture that holds up well to cooking, which is why they're the plum of choice for drying into prunes as well as for jams, compotes, tarts, and cakes. Their tartness varies with ripeness and can balance the richness of meats like duck and pork in some Eastern European dishes, such as Hungarian plum dumplings (szilvás gombóc). Choose plums that are firm with even, unblemished color and a slight give when gently squeezed; they keep at room temperature for a few days or refrigerated for about a week.