Extra juicy plums with that unique tart and sweet taste range from golden yellow to the deepest purple. That tartness allows them to be used freely in both sweet and savory dishes including tarts, cobblers, preserves, and a classic Chinese plum sauce for meat and poultry. Plums should feel plump in your hand and not too hard - they do ripen at room temperature if you leave them out, but tree-ripened plums will be much sweeter.