Black hammer is a variety of plum that gets its name from the black, slightly tart skin and juicy amber-colored flesh. Compared to other dark-skinned plums, the ‘Black hammer’ has firm flesh and distinct tartness to the taste. The round plums have a bluish appearance due to the waxy coating that covers most types of prunes. This plum cultivar is usually ripe for eating in mid- to late summer. You can use this plum in cooking as its firm flesh and sweet-sour taste adds flavor and texture to many dishes.