How to choose: Santa Rosas should be slightly soft and fragrant. If there are white spots on the skin, don't worry. Those are just naturally occurring yeasts that have collected there. Actually, it's a good indicator that the fruit hasn't been overhandled.
How to store: If they're a little too firm, leave plums at room temperature for a day or two and they'll continue to ripen. Once they're fully ripe, refrigerate them.
How to prepare: Plums make terrific crisps--chop them, sweeten them with a little sugar and toss with a little flour or cornstarch to thicken the juices. Put the plums in a baking dish and top with a crumbly mixture of ¼ cup butter, ½ cup flour and ¼ cup sugar that you've cut together in a bowl or in a food processor. Bake at 350 degrees until the fruit is melted and fragrant and the topping has browned and crisped.